At 8:46 in the morning of September 11, 2001, American Airlines Flight 11 struck the North Tower of the World Trade Center in New York City at approximately 470 miles per hour. The impact, felt across lower Manhattan, was initially reported as a possible small aircraft accident. Seventeen minutes later, at 9:03, United Airlines Flight 175 struck the South Tower, and whatever ambiguity remained about what was happening dissolved instantly for everyone watching. By 10:03, when United Airlines Flight 93 crashed into a field near Shanksville, Pennsylvania, after passengers attempted to overpower the hijackers, four aircraft had been turned into weapons, both World Trade Center towers had collapsed, the Pentagon had been struck, and 2,977 people were dead.
September 11 was the deadliest terrorist attack in history and the deadliest attack on American soil since Pearl Harbor. Its consequences extended far beyond its immediate death toll: it reshaped American foreign policy for at least two decades, initiated the War on Terror that killed hundreds of thousands of people across Afghanistan, Iraq, and elsewhere, produced the surveillance and security apparatus that transformed daily life for hundreds of millions of people globally, and altered the relationship between Western democracies and their Muslim-minority populations in ways whose political consequences are still accumulating. To trace the arc from Al-Qaeda’s formation through the attacks themselves to the transformations of American domestic and foreign policy that followed is to follow the event that more than any other defined the twenty-first century’s opening decades.
Al-Qaeda and the Road to September 11
Al-Qaeda, whose name means “the base” in Arabic, grew from the networks that had been built during the Soviet-Afghan War of 1979-1989. The Arab volunteers who had come to Afghanistan to fight the Soviet occupation, financed and organised partly by Saudi intelligence and by wealthy Gulf donors, gained combat experience, developed transnational networks, and absorbed a theology of global jihad that the Afghan experience seemed to validate: a Muslim people, supported by Muslims from across the world, had defeated a superpower. The conclusion that some drew, that jihadist resistance could be effective even against the world’s most powerful conventional military, became the foundation of Al-Qaeda’s strategic vision.
Osama bin Laden, a Saudi from a wealthy construction family who had come to Afghanistan in 1980 and had provided both money and logistics for Arab volunteers, formed Al-Qaeda in 1988 with the specific objective of continuing the jihad beyond Afghanistan. His ideological framework, developed in collaboration with Ayman al-Zawahiri (whose Egyptian Islamic Jihad merged with Al-Qaeda in the late 1990s), identified the United States as the “far enemy” whose presence in the Arabian Peninsula since the Gulf War, and whose support for Israel and Arab secular governments, made it the primary target rather than the “near enemies” of individual Arab regimes.
The theological and strategic innovation that distinguished Al-Qaeda from previous Islamist movements was the targeting of the “far enemy” United States directly, rather than the Arab governments that American support sustained. Previous Islamist movements, including the Egyptian Islamic Jihad and the Algerian GIA, had focused on overthrowing their own governments; their consistent failure, partly because those governments had American backing, led Zawahiri and bin Laden to conclude that the head of the snake had to be struck rather than the body. This analysis, however strategically misconceived its ultimate effects proved to be, drove the global terror campaign that September 11 represented.
Al-Qaeda’s operational history before September 11 included the 1993 World Trade Center bombing (by a network affiliated with but distinct from Al-Qaeda proper), the 1996 Khobar Towers bombing in Saudi Arabia that killed nineteen American soldiers, the 1998 simultaneous bombings of American embassies in Kenya and Tanzania that killed 224 people, and the 2000 attack on USS Cole in Yemen that killed seventeen sailors. Each attack demonstrated increasing operational capability and increasing willingness to accept casualties, and the Cole attack in particular reflected a direct strike on American military power that anticipated September 11’s targeting logic.
The United States’ response to these earlier attacks was limited in ways that Al-Qaeda interpreted as evidence of American unwillingness to absorb casualties. The Clinton administration launched cruise missile strikes on Al-Qaeda camps in Afghanistan following the embassy bombings, but the strikes killed approximately twenty people and missed bin Laden, producing the humiliation of appearing to shoot millions of dollars of missiles at $10 tents. The response to the Cole attack was essentially nothing beyond an FBI investigation, a restraint that bin Laden publicly cited as evidence that America could be hit without effective retaliation.
The Planning of the Attacks
The September 11 operation, designated “the planes operation” within Al-Qaeda, was planned over approximately four years, involving the coordination of nineteen hijackers, the selection of targets, the logistics of flight training, and the financing of an operation that cost approximately $400,000 to $500,000.
Mohamed Atta, an Egyptian who had become radicalised in Hamburg while completing a doctorate, was selected as the operational commander of the attacks. His engineering background, meticulous planning, and absolute commitment to the operation’s objectives made him the most capable of the hijackers for the leadership role. He and several other cell members studied architecture and urban planning specifically to assess the World Trade Center’s structural vulnerabilities, a level of preparation that reflected the operation’s years of development.
The nineteen hijackers were divided into four teams, one for each aircraft, with Atta commanding the Flight 11 team. Fifteen of the nineteen were Saudi nationals, a composition that reflected both Al-Qaeda’s predominantly Saudi foreign fighter network and bin Laden’s calculation that Saudi nationals would face less scrutiny at American immigration than nationals from countries more associated with terrorism in American intelligence assessments.
The choice of targets reflected both practical and symbolic considerations. The World Trade Center towers were the most visible symbols of American financial power; the Pentagon was the centre of American military power; and the fourth aircraft, believed to be targeting either the Capitol or the White House, would have struck the centre of American political power. The operation was designed to demonstrate simultaneously that Al-Qaeda could strike at the heart of America’s financial, military, and political systems, creating a psychological effect of vulnerability disproportionate to even the enormous physical damage the attacks caused.
The flight training that the hijackers received at American flight schools was the most practically challenging element of the operation. Several hijackers, including Atta and his Hamburg cell associates, trained at flight schools in Florida, learning to fly commercial aircraft through a process that required years of preparation. The choice to train in the United States rather than elsewhere reflected the availability and quality of American flight training and the assumption that foreign nationals training on commercial aircraft would not attract the kind of surveillance that might compromise the operation.
The American intelligence community’s failure to detect the operation, despite several signals that were available in retrospect, is one of the most thoroughly analysed intelligence failures in history. The 9/11 Commission identified specific failures including the failure to share information between the CIA and FBI, the absence of the sustained analytical focus on Al-Qaeda that the threat warranted, and the institutional disconnections that prevented the specific information about Arab nationals taking flight training from connecting to the broader intelligence picture of Al-Qaeda’s planning. The Phoenix Memo, written by an FBI agent in July 2001 warning that Al-Qaeda might be training pilots at American flight schools, was not acted upon. The CIA had information about two of the eventual hijackers in the United States but did not share it with the FBI in time for preventive action.
September 11: The Attacks
The four hijackings occurred within thirty minutes of each other on the morning of September 11, all on flights departing from Boston’s Logan Airport, Newark’s Liberty Airport, and Washington’s Dulles Airport. The timing, on a weekday morning when the chosen cross-country flights would be relatively full of fuel but relatively lightly loaded with passengers, reflected careful operational planning.
American Airlines Flight 11, bound from Boston to Los Angeles with ninety-two people aboard, was hijacked approximately fifteen minutes after takeoff. The hijackers used box cutters to kill two flight attendants and stabbed a passenger who tried to resist; they may also have used a chemical irritant. The hijackers, led by Atta, took control of the flight and turned it south toward New York. At 8:46, it struck the North Tower between the 93rd and 99th floors at approximately 440 miles per hour.
United Airlines Flight 175, also from Boston to Los Angeles with sixty-five people aboard, was hijacked approximately thirty minutes after takeoff. At 9:03, it struck the South Tower between the 77th and 85th floors. The impact was witnessed live on television by millions of people who had been watching coverage of the North Tower fire, and the visual evidence that this was a deliberate attack removed any remaining ambiguity about what was happening.
American Airlines Flight 77, from Washington Dulles to Los Angeles with sixty-four people aboard, turned around over Ohio and flew back toward Washington. At 9:37, it struck the western face of the Pentagon at approximately 530 miles per hour, killing 125 people in the building in addition to the sixty-four aboard the aircraft.
United Airlines Flight 93, from Newark to San Francisco with forty-four people aboard, was the fourth hijacked aircraft. Its delay in departure gave passengers time to receive phone calls from family members who had heard about the other attacks, providing them with information the earlier hijacked aircraft’s passengers had not possessed. Understanding that the aircraft was being turned into a weapon, passengers organised and attempted to take back control of the aircraft. The cockpit voice recorder captured the sounds of the struggle; the aircraft, clearly being fought over, crashed into a field near Shanksville, Pennsylvania at 10:03, killing all forty-four aboard. The intended target, almost certainly either the Capitol or the White House, was not reached.
The Collapse and Immediate Aftermath
The collapse of the World Trade Center towers was not simply the consequence of the aircraft impacts but reflected the specific engineering interaction of the impacts, the fire, and the buildings’ structural design. The South Tower collapsed at 9:59, fifty-six minutes after being struck. The North Tower collapsed at 10:28, one hour and forty-two minutes after being struck. The collapse of each tower produced a massive dust cloud that enveloped lower Manhattan and drove thousands of people through the streets.
2,977 people were killed in the attacks and the subsequent collapses, not counting the nineteen hijackers. The deaths were distributed across the aircraft, the World Trade Center towers and the surrounding area, and the Pentagon. Among the dead were 343 firefighters and 72 police officers who had entered the buildings to evacuate occupants and who were killed when the towers collapsed. The specific distribution of deaths, across nationalities, professions, and circumstances, made September 11 a genuinely collective catastrophe rather than a targeted assassination: the victims included people of sixty-plus nationalities, from janitors to financial executives, and the randomness of who died and who survived, determined by whether one’s office was above or below the impact floors, what stairwell one chose to escape by, and whether one had arrived at work yet that morning, communicated the indiscriminate character of the violence.
The federal government’s emergency response included the grounding of all civilian aircraft in the United States, the first time in American aviation history that the entire national airspace had been shut down. The Secret Service evacuated the White House and the Capitol. President Bush, who was reading to schoolchildren in a Florida classroom when the attacks began, was kept airborne on Air Force One for hours before landing at Barksdale Air Force Base in Louisiana and then Offutt Air Force Base in Nebraska while the security situation was assessed.
Bush’s bullhorn speech at Ground Zero on September 14, standing on the rubble with firefighters and holding a bullhorn to address rescue workers, communicated a presidential resolve and personal presence that his initial response had not conveyed. His statement that those responsible would “hear from us” was understood as a declaration of military response, which the subsequent days confirmed.
The Human Experience
The human experience of September 11 was defined by the intersection of the catastrophic with the intimate: thousands of people died, but their deaths occurred in ways that were visible in real time, that produced thousands of individual stories of survival and loss, and that were experienced both directly by those in New York, Washington, and Shanksville and vicariously through the television coverage that made the attacks a shared national experience in ways that no previous disaster had achieved.
The people who jumped from the upper floors of the World Trade Center towers, unable to survive the fire and smoke that the impacts had created and choosing their manner of death rather than having it imposed, represented the attack’s most agonising visual dimension. The Associated Press photographs of people falling from the towers, including the photograph known as “The Falling Man,” were initially published and then largely removed from circulation as the news cycle processed the impossible ethical question of how to report on deaths of this character.
The phone calls that passengers on the hijacked aircraft and people trapped in the towers made to family members, documented in the 9/11 Commission’s report and in subsequent memoir accounts, are among the most intimate documents of mass disaster that modern technology has produced. The calls combined expressions of love with practical information; some callers described what they could see; some left final messages on answering machines that their families have preserved and have struggled to decide how to process. The specific character of these calls, made in moments of absolute terror with the knowledge that they might be the last communication, captures something about the attack’s human meaning that casualty statistics cannot.
The first responders who entered the buildings knowing they might not get out, who continued going up the stairwells as thousands of occupants came down, and who were killed when the towers collapsed, represent the attack’s most discussed dimension of individual courage. The 343 firefighters who died were a significant fraction of the New York City Fire Department’s institutional community; their deaths, concentrated in specific firehouses whose entire crews were lost together, created grief that spread through communities and families in ways that the FDNY has processed publicly through memorials and commemorations in the years since.
The Bush Administration’s Response
George W. Bush’s response to September 11 defined his presidency and reshaped American foreign policy in ways whose consequences extended far beyond his two terms in office.
His immediate response combined genuine shock, the attacks had not been anticipated by the intelligence community’s most senior briefings in the days before September 11, with the clarity of purpose that the attacks’ scale demanded. His September 20, 2001 address to a joint session of Congress, nine days after the attacks, was the most watched television address in American history to that point, and its framing of the response as a “war on terror” established the conceptual framework within which American policy would operate for the following two decades.
The framing of the response as a “war” was consequential in ways that its authors may not have fully anticipated. War invokes legal authorities, institutional structures, and policy frameworks that differ from those available for law enforcement or intelligence responses; it authorises the use of military force; it creates the framework for military detention and military trial; and it suggests a binary enemy-combatant structure that does not map cleanly onto the diffuse, transnational, ideologically motivated network that Al-Qaeda actually was. The war framing produced both genuine capabilities for pursuing Al-Qaeda’s leadership and the institutional deformations, including the detention centre at Guantánamo Bay, the authorisation of “enhanced interrogation techniques” (which the Senate Intelligence Committee subsequently characterised as torture), and the surveillance expansion that the PATRIOT Act authorised.
Afghanistan: The First War
The October 2001 military campaign in Afghanistan, Operation Enduring Freedom, was the most directly justified military response in the War on Terror’s history: Al-Qaeda’s leadership and training infrastructure were in Afghanistan under Taliban protection, and the Taliban government’s refusal to surrender bin Laden gave the invasion both the specific military target and the broad international support that subsequent War on Terror operations would lack.
The initial campaign, which combined American and British air power with the Northern Alliance’s ground forces and small numbers of CIA and special operations personnel, achieved a remarkable military success in approximately two months. The Taliban government collapsed; its forces retreated from Kabul and other cities; bin Laden escaped through the mountains near Tora Bora in December 2001 into Pakistan in a missed opportunity that subsequent critics have attributed to excessive reliance on Afghan proxy forces rather than American troops for the direct pursuit.
The failure to capture or kill bin Laden at Tora Bora had operational and political consequences that extended well beyond the immediate military failure. The Al-Qaeda leadership’s escape into Pakistan established the specific geography of the threat that American operations in Afghanistan would never adequately address: the Taliban and Al-Qaeda’s leadership were in Pakistan, whose intelligence services had created the Taliban and retained relationships with its leadership that made genuine cooperation in the War on Terror impossible despite Pakistan’s official alliance with the United States.
Key Figures
Osama bin Laden
Bin Laden’s strategic vision, his operational patience, and his specific understanding of how to use spectacular violence to mobilise Muslim opinion and generate American overreaction, made him the most consequential individual terrorist in history. His September 11 planning reflected a calculation that a sufficiently dramatic attack on American soil would produce an American military response in the Muslim world that would, in turn, radicalise Muslim populations and eventually produce the global jihad that Al-Qaeda sought.
This calculation was partly right and partly catastrophically wrong. The American response did produce military action in two Muslim-majority countries; it did generate significant anti-American sentiment in the Muslim world and a degree of radicalisation that subsequent events in Iraq in particular amplified. But it did not produce the Muslim uprising that bin Laden envisioned, partly because most Muslims, including most conservative Muslims, found Al-Qaeda’s theology and tactics unacceptable, and partly because the September 11 attacks, which killed people of numerous Muslim nationalities among their victims, were not the galvanising event for Muslim solidarity that bin Laden had predicted.
His killing by Navy SEAL Team Six at his compound in Abbottabad, Pakistan on May 2, 2011, almost ten years after the attacks, was one of the most consequential military operations of the War on Terror period. His death decapitated Al-Qaeda’s leadership and eliminated the most significant individual in the global jihadist movement, though the movement’s diffusion and the emergence of ISIS meant that his death did not end the threat he had helped create.
Khalid Sheikh Mohammed
KSM, as he is referred to in intelligence and legal documents, was the operational mastermind of September 11: the person who brought the planes operation to bin Laden, who managed its logistics, who recruited and trained the hijackers, and who coordinated the hundreds of details that the operation’s execution required. His career as a terrorist planner included an extraordinary range of plots, from the Bojinka Plan (a 1995 plan to bomb twelve American aircraft over the Pacific that was disrupted) through numerous other operations that were executed or disrupted.
His capture in Pakistan in March 2003 and his subsequent detention and interrogation at CIA black sites, where he was waterboarded 183 times according to Senate Intelligence Committee documents, produced significant intelligence information about Al-Qaeda’s structure, personnel, and operations, as well as significant controversy about the methods used to obtain it. The question of whether the intelligence obtained through what the CIA called “enhanced interrogation techniques” could have been obtained through other means, and whether those techniques constituted torture prohibited by the UN Convention Against Torture and the Geneva Conventions, has been one of the most persistent ethical and legal debates of the post-September 11 era.
George W. Bush
Bush’s presidency was defined by September 11 from its first year, and the decisions he made in the attacks’ immediate aftermath established the architecture of the American response that outlasted his administration. His decision to pursue the War on Terror as a military rather than primarily a law enforcement and intelligence matter, his approval of “enhanced interrogation techniques,” his decision to invade Iraq in 2003 on the basis of intelligence about weapons of mass destruction that proved inaccurate, and his authorisation of the NSA surveillance programmes that Edward Snowden revealed in 2013, all reflected the specific choices of a president governing under the traumatic conditions of the attacks and under the institutional pressures of a national security establishment convinced that further attacks were imminent.
His public communication in the immediate aftermath of the attacks, including his September 20 address and his bullhorn speech at Ground Zero, was among the most effective presidential communication in modern American history, expressing the combination of shared grief, determination, and solidarity that the situation required. His subsequent decisions, particularly the Iraq War and the authorisation of torture, produced consequences that his administration did not adequately anticipate and that his historical legacy has been unable to escape.
The Domestic Transformation
September 11’s transformation of American domestic life and governance extended well beyond the initial emergency response to produce lasting changes in the security apparatus, civil liberties framework, and political culture that define American public life to the present.
The USA PATRIOT Act, passed by Congress six weeks after the attacks, expanded the federal government’s surveillance authorities dramatically, reducing judicial oversight of intelligence gathering, expanding the definition of “terrorism” to include a broader range of activities, and authorising “sneak and peek” searches that could be conducted without immediately notifying the target. The Act passed with minimal Congressional debate, reflecting the political atmosphere in which opposing any security measure could be characterised as indifference to the attacks’ lessons.
The Department of Homeland Security, established in November 2002 and combining twenty-two federal agencies into a single cabinet department, was the largest reorganisation of the American federal government since the National Security Act of 1947. Its creation reflected the assessment that the September 11 intelligence and coordination failures required institutional reform, though the subsequent management challenges of integrating organisations with very different institutional cultures and missions demonstrated that reorganisation does not automatically produce the coordination it is designed to achieve.
The Transportation Security Administration, which took over airport security from private contractors, produced the screening procedures, body scanners, and travel documentation requirements that have made air travel qualitatively different from the pre-September 11 experience. The changes, which affect hundreds of millions of air travellers annually, represent the most directly experienced daily consequence of September 11 for the majority of Americans and international travellers who do not follow national security policy closely but do take off their shoes at airport security lines.
The surveillance expansion that the NSA conducted under the PRISM programme and related authorities, revealed by Edward Snowden’s 2013 disclosures, demonstrated the scale to which the post-September 11 security apparatus had grown. The collection of telephone metadata on essentially all American phone calls, the interception of internet communications, and the relationships with technology companies that the programme required, reflected a security establishment that had grown around the September 11 mandate in ways that extended well beyond what the original authorisations had anticipated.
The International Dimension
September 11’s international dimension reflected both the genuine multinational character of the attacks’ victims, who came from more than sixty countries, and the profound effect on American foreign policy that produced the specific international relationships and conflicts that defined the 2000s.
The immediate international response was one of exceptional solidarity. NATO invoked Article 5, the collective defence provision, for the first time in the alliance’s history, treating September 11 as an attack on all member states. Countries from Germany to Pakistan expressed genuine condolences; even Iran’s supreme leader issued a statement of sympathy. The specific UN Security Council resolutions that authorised the Afghanistan operation passed with broad international support, reflecting the near-universal assessment that Al-Qaeda’s attack constituted a threat to international security requiring a collective response.
This solidarity was subsequently squandered by the Iraq War decision, which divided the international community as sharply as September 11 had united it. The Bush administration’s argument that Iraq posed a similar threat to September 11, through its alleged weapons of mass destruction and its alleged connections to Al-Qaeda, was rejected by key allies including France, Germany, and Russia, and the decision to invade without UN authorisation produced the most serious split in Western alliance relationships since Suez. The failure to find weapons of mass destruction after the invasion, and the subsequent chaos of the occupation, converted the sympathy that September 11 had generated into the specific scepticism about American strategic judgment that defined international relations for the following decade.
The Iraq War and Its Relationship to September 11
The relationship between September 11 and the 2003 Iraq War is one of the most consequential and most contested questions in recent American foreign policy history. The attacks were used to justify the Iraq War without there being a genuine operational connection between them, and the subsequent conflation of the two in American public opinion was both a product of the Bush administration’s deliberate messaging strategy and a reflection of the specific psychological dynamics of post-September 11 America.
The September 11 Commission’s final report, published in July 2004, found no credible evidence of a collaborative operational relationship between Saddam Hussein’s Iraq and Al-Qaeda. The intelligence that the administration cited for Iraqi weapons of mass destruction was, as the subsequent investigations of the Senate Intelligence Committee and the Butler Review in Britain established, based on flawed analysis and unreliable human intelligence that was not adequately scrutinised. The specific intelligence failure was not simply a matter of the CIA getting it wrong but of an analytical process that had been shaped by the political pressure for a specific conclusion.
The Iraq War’s consequences for the War on Terror were broadly negative. The invasion and occupation created the conditions in which Al-Qaeda in Iraq grew from a minor presence to a major force, as the post-invasion chaos, the disbanding of the Iraqi army, and the de-Baathification process that excluded Sunni officials from the new government all provided recruitment and organisational conditions that Al-Qaeda exploited. The specific insurgency that developed in Iraq, which killed thousands of American soldiers and hundreds of thousands of Iraqis between 2003 and 2011, was a direct product of the invasion that September 11 was used to justify.
The Long-Term Consequences
September 11’s long-term consequences are still unfolding, but several dimensions have already reshaped American and global politics in ways that are unlikely to be reversed.
The reconfiguration of American security spending around the terrorism threat, while producing genuine capabilities for disrupting terrorist operations, also reflected the institutional momentum of a security establishment that had grown to justify its own expansion. The annual US intelligence budget, which was approximately $40 billion before September 11, grew to over $80 billion by the mid-2000s. The specific cost of the War on Terror, estimated by various analyses at between $4 trillion and $6 trillion when veterans’ healthcare and long-term costs are included, produced the fiscal consequences that subsequent economic and budget debates had to address.
The impact on Muslim-American communities and on Muslim communities globally was one of the attacks’ most painful and least discussed consequences. The profiling, surveillance, and social suspicion that September 11 directed toward Muslim Americans, the travel restrictions on people from Muslim-majority countries, and the anti-Muslim bigotry that both the attacks and the subsequent wars enabled created a specific burden for communities that were simultaneously victims of the attack (Muslim Americans were among the dead) and subjects of the suspicion it generated.
The broader cultural impact of September 11 on American life, on the American understanding of vulnerability, on the political culture of a country that had not experienced a major attack on its own territory since Pearl Harbor, produced psychological and cultural changes that are more difficult to measure than policy changes but equally real. The specific quality of American life in the years after September 11, the colour-coded threat levels, the heightened vigilance at public spaces, and the persistent background awareness of potential attack, represented a transformation in the social psychology of a society that had previously been largely insulated from the terrorism experience that other countries had lived with for decades.
Frequently Asked Questions
Q: Who carried out the September 11 attacks and why?
The September 11 attacks were carried out by nineteen members of Al-Qaeda, led by Mohammed Atta in the operational role and planned and directed by Khalid Sheikh Mohammed under Osama bin Laden’s overall command. Fifteen of the nineteen hijackers were Saudi nationals; the others were from the United Arab Emirates, Egypt, and Lebanon. Their motivation was Al-Qaeda’s specific ideology, which held that the United States was the primary enemy of Islam because of its military presence in the Arabian Peninsula, its support for Israel, and its backing of Arab secular governments that Al-Qaeda considered apostate. Bin Laden’s specific strategic calculation was that a spectacular attack on American soil would draw the United States into military operations in the Muslim world that would, in turn, radicalise Muslim populations and generate the conditions for a global Islamic uprising. This strategic vision was based on the lesson Al-Qaeda drew from the Soviet-Afghan War: that jihadist resistance had defeated a superpower before and could do so again.
Q: What happened on September 11, step by step?
On the morning of September 11, 2001, nineteen Al-Qaeda operatives hijacked four commercial aircraft on the East Coast of the United States. At 8:46 AM Eastern time, American Airlines Flight 11 struck the North Tower of the World Trade Center in New York City. At 9:03, United Airlines Flight 175 struck the South Tower. At 9:37, American Airlines Flight 77 struck the Pentagon in Arlington, Virginia. At 9:59, the South Tower collapsed; at 10:03, United Airlines Flight 93, whose passengers had learned of the other attacks and attempted to overpower the hijackers, crashed into a field near Shanksville, Pennsylvania. At 10:28, the North Tower collapsed. 7 World Trade Center, a building adjacent to the Twin Towers that had been severely damaged by the collapse, also fell later that day. In total, 2,977 people were killed in addition to the nineteen hijackers.
Q: Why did the World Trade Center towers collapse?
The World Trade Center towers collapsed because of the specific combination of structural damage from the aircraft impacts and the fires that burned at temperatures sufficient to weaken the steel structural elements that supported the floors. The aircraft impacts did not immediately destroy the towers, which continued to stand for approximately 56 minutes (South Tower) and 102 minutes (North Tower) after being struck. The fires, fuelled by the aircraft’s jet fuel and by the contents of the offices, burned at temperatures that weakened the steel floor trusses until they could no longer support the weight of the floors above the impact zone. When the upper sections began to collapse, the momentum of their fall was sufficient to produce the progressive collapse of the entire structure. The specific design of the towers, which used an innovative open-floor plan supported by the exterior walls and a central core, contributed to the progressive collapse’s speed once it began.
Q: What was Al-Qaeda and how did it develop?
Al-Qaeda was a Sunni Islamist militant organisation founded by Osama bin Laden in 1988, during or immediately after the Soviet-Afghan War, with the objective of continuing the global jihad beyond Afghanistan. Its ideology combined a specific interpretation of Salafi Islamic theology with a Third World anti-colonial political framework, identifying the United States as the primary enemy of Islam because of its military presence, its support for Israel, and its backing of Arab secular governments. Al-Qaeda developed from the Arab volunteer networks that had fought in Afghanistan, and it retained both the organisational infrastructure those networks had created and the theological framework that the Afghan jihad’s apparent success against the Soviet Union had seemed to validate. Before September 11, Al-Qaeda conducted attacks including the 1998 American embassy bombings in Kenya and Tanzania and the 2000 attack on USS Cole. After September 11, the American-led invasion of Afghanistan destroyed Al-Qaeda’s Afghan infrastructure and killed or captured much of its leadership, forcing the organisation to decentralise; its affiliates and inspired networks have conducted subsequent attacks globally.
Q: What was the US government’s response to the attacks?
The US government’s response to September 11 was comprehensive and multidimensional. Domestically, Congress passed the USA PATRIOT Act, which expanded surveillance authorities; the Department of Homeland Security was created to coordinate domestic security; the Transportation Security Administration was established to take over airport security; and the NSA expanded its collection of communications data under new legal authorities. Militarily, the United States invaded Afghanistan in October 2001, overthrowing the Taliban government that had harboured Al-Qaeda and killing or capturing much of Al-Qaeda’s senior leadership, though bin Laden escaped. In 2003, the US invaded Iraq, arguing that Saddam Hussein’s alleged weapons of mass destruction and alleged connections to Al-Qaeda made Iraq part of the War on Terror, a decision that the subsequent failure to find weapons of mass destruction and the chaos of the occupation rendered highly controversial. The National Security Agency conducted surveillance programmes of unprecedented scale under new legal authorities, some of which were revealed as going beyond what the authorising laws permitted when Edward Snowden disclosed them in 2013.
Q: What was the 9/11 Commission and what did it find?
The National Commission on Terrorist Attacks Upon the United States, known as the 9/11 Commission, was established by President Bush and Congress in November 2002 to investigate the circumstances of the attacks and recommend improvements to prevent future attacks. Co-chaired by former New Jersey Governor Thomas Kean and former Congressman Lee Hamilton, the commission conducted the most extensive investigation into an American national security failure in history, reviewing approximately 2.5 million documents and conducting approximately 1,200 interviews. Its report, published in July 2004, found that the attacks resulted from failures of imagination (the inability to conceive that terrorists would use aircraft as weapons), policy (inadequate responses to the Al-Qaeda threat before September 11), capability (specific weaknesses in intelligence collection and analysis), and management (failure to share information between agencies and to create the coordination mechanisms that the threat required). The commission made 41 recommendations, most of which were subsequently implemented through the Intelligence Reform and Terrorism Prevention Act of 2004, which created the Director of National Intelligence position to coordinate the sixteen intelligence agencies.
Q: Were there warnings before the attacks that were missed?
Yes, there were significant warnings that Al-Qaeda was planning a major attack, and the intelligence community’s failure to act on them was one of the 9/11 Commission’s most important findings. In August 2001, President Bush received a Presidential Daily Brief titled “Bin Laden Determined to Strike in US” that described Al-Qaeda’s intent to conduct attacks in the United States, including airline hijackings. An FBI agent in Phoenix had sent a memo in July 2001 warning that Al-Qaeda might be training pilots at American flight schools. The CIA had information about two of the eventual hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, who were in the United States, but failed to share this information with the FBI in time for the latter to locate them. The NSA had intercepted communications indicating an impending major attack but the specific date and target were not identified. The failures reflected a combination of institutional barriers to information sharing between agencies, inadequate analytical resources devoted to the Al-Qaeda threat, and the specific failure of imagination that the 9/11 Commission identified as the most fundamental problem.
Q: What was the impact on Muslim Americans and Muslim communities globally?
The impact of September 11 on Muslim Americans was one of the attacks’ most painful dimensions. Muslim Americans, who were among the nearly 3,000 victims, were simultaneously affected by the same grief, fear, and determination to understand what had happened as all Americans, and were additionally subjected to the backlash that the attacks’ attribution to Muslim terrorists generated. In the weeks following September 11, the FBI reported approximately 500 hate crimes against Muslims, Arabs, and people perceived as Muslim or Arab, including murders, assaults, and arson attacks on mosques. Hundreds of Muslim men were detained and questioned by federal authorities in the months after the attacks; some were held for extended periods without charge; the legal authorities under which these detentions occurred were challenged in subsequent litigation. The surveillance of Muslim communities by law enforcement and intelligence agencies, conducted under what the NYPD’s Demographics Unit programme represented, produced what civil liberties organisations characterised as a system of monitoring based on religious identity rather than evidence of wrongdoing.
Q: How did September 11 change air travel and airport security?
September 11’s impact on air travel and airport security was immediate and permanent. The Transportation Security Administration replaced private airport security contractors and implemented new screening procedures that have made air travel qualitatively different from the pre-September 11 experience. Passengers are required to remove shoes, belts, and jackets; to remove laptops and liquids from carry-on bags; to pass through body scanners or metal detectors; and to show government identification. Cockpit doors were reinforced and locked from the inside. Air marshals were deployed on a larger proportion of flights. International travellers to the United States became subject to additional scrutiny including biometric data collection and pre-screening processes. The economic cost of these security measures, including the time cost imposed on hundreds of millions of travellers annually, has been estimated in the tens of billions of dollars. The effectiveness of specific screening measures, and the trade-off between security and the civil liberties and convenience of the travelling public, has been the subject of sustained debate that the Transportation Security Administration has managed imperfectly.
Q: What happened to the site of the World Trade Center?
The World Trade Center site, known as Ground Zero in the immediate aftermath, became the focus of a contentious and prolonged design and rebuilding process that lasted over a decade and reflected both the commercial pressures of redeveloping one of the world’s most valuable pieces of real estate and the memorial pressures of honouring thousands of dead on a site that many survivors and victims’ families regarded as sacred ground. The 9/11 Memorial, designed by Michael Arad and Peter Walker, was opened on September 11, 2011, the tenth anniversary of the attacks, and features two large reflecting pools occupying the footprints of the original towers, with the names of all 2,977 victims inscribed around their edges. The 9/11 Memorial Museum, built in the bedrock beneath the memorial pools, opened in May 2014 and houses extensive documentation of the attacks including recovered artefacts, testimony, and historical documentation. One World Trade Center, at 1,776 feet the tallest building in the Western Hemisphere, was completed in 2014 and opened to tenants in 2014, restoring commercial office space to the site that had been destroyed.
Q: What is the ongoing legacy of September 11 for global security?
September 11’s legacy for global security is measured primarily through the War on Terror’s two-decade history, which produced both genuine achievements in disrupting Al-Qaeda’s operational capability and specific strategic failures that created new threats and new instabilities. The genuine achievements included the capture or killing of a large proportion of Al-Qaeda’s original leadership, including bin Laden, the destruction of the Afghan training infrastructure that had prepared the September 11 hijackers, and the development of international intelligence and law enforcement cooperation mechanisms that have disrupted numerous subsequent plots. The strategic failures included the Iraq War’s creation of the conditions in which ISIS emerged, the Afghan War’s failure to produce a stable democratic government after twenty years, and the surveillance expansion that normalised mass collection of communications data in ways that subsequent legal frameworks have not adequately constrained.
The lessons history teaches from September 11 about the limits of military power as an instrument for addressing the specific threat of transnational terrorism, about the institutional costs of security expansion without adequate democratic oversight, and about the long-term consequences of foreign policy decisions made under the psychological conditions of a traumatic attack, are among the most important available for understanding the security environment that the twenty-first century has produced. The attacks that began September 11’s long aftermath have not ended, and the frameworks that September 11 created for understanding and responding to terrorism continue to shape the choices that governments make about how to balance security and freedom.
Q: What was the cultural impact of September 11 on American society?
September 11’s cultural impact on American society has been pervasive and enduring, reshaping not only policy but the texture of daily life, the cultural products that the society generates, and the psychological background against which Americans understand their place in the world.
The immediate cultural response combined genuine collective grief with a nationalism that expressed itself in flag displays, public solidarity, and a temporary suspension of the political divisions that had been intensifying since the 2000 election’s controversial resolution. This unity was genuine but brief: within months, the political divisions that the security measures produced, and the decision to invade Iraq, had restored and in some respects deepened the divisions that September 11 had briefly suspended.
The cultural products that September 11 generated, from documentary films and fiction to memorial architecture and civic rituals, have tried to address both the event itself and the questions it raised about America’s place in the world, about the relationship between security and freedom, and about what the deaths of nearly 3,000 people should mean for how a society conducts itself. The annual commemorations on September 11, which balance public acknowledgment of loss with the forward-looking civic life of a democracy, have produced both the necessary ritual of collective memory and the political tensions that arise when tragedy becomes the object of competing interpretations.
The specific change in American consciousness about vulnerability, from the relative security of a country that had not been attacked on its own soil since 1941, to the awareness that mass casualty attacks were possible and had occurred, was one of September 11’s most fundamental cultural consequences. Whether this awareness made American public policy wiser or more fearful is a question that the subsequent decades’ history has answered ambiguously, providing evidence for both the cases that fear produced necessary precautions and that fear enabled unnecessary and costly overreactions.
Q: How did September 11 affect the relationship between civil liberties and security in America?
September 11’s most lasting domestic legacy may be its transformation of the relationship between civil liberties and security, as the emergency authorities claimed in the attacks’ aftermath have proved far more durable than the specific emergency that justified them.
The PATRIOT Act’s expansions of surveillance authority, initially justified as temporary emergency measures, were repeatedly reauthorised and in some cases made permanent. The legal frameworks for military detention, for the use of military commissions to try terrorism suspects, and for the surveillance of communications both within and beyond the United States, were developed in the years following September 11 and have been modified but not abandoned under subsequent administrations.
The detention facility at Guantánamo Bay, which at its peak held approximately 780 detainees, became the most visible symbol of the specific legal framework that September 11 produced. The administration’s argument that detainees were “enemy combatants” who were entitled neither to prisoner of war status under the Geneva Conventions nor to the constitutional rights of criminal defendants created a category of legal limbo that the Supreme Court partially addressed in a series of decisions, including Hamdan v. Rumsfeld (2006), which required some measure of legal process, and Boumediene v. Bush (2008), which extended habeas corpus rights to Guantánamo detainees.
The specific tension between the security state’s expansion and the civil liberties that American democracy was founded to protect has produced the most important domestic constitutional debate of the post-September 11 era. The ACLU, civil liberties advocates in Congress, and eventually Supreme Court decisions have all contested aspects of the post-September 11 security architecture. The question of where the appropriate balance lies between security and freedom, and whether the measures adopted in the emergency of September 11 are appropriate for the sustained counter-terrorism effort that the threat requires, is one that American democracy continues to debate without reaching a stable answer.
Q: What was the role of Saudi Arabia and what did the 28 pages reveal?
Saudi Arabia’s relationship to September 11 is one of the most contested dimensions of the attacks’ history, involving both the nationality of fifteen of the nineteen hijackers and allegations about connections between the Saudi government and Al-Qaeda financing that were investigated and partially suppressed.
The “28 pages” referred to the redacted portion of the joint congressional inquiry into September 11’s intelligence failures, which investigated potential connections between the Saudi government and the September 11 hijackers. The pages, which were declassified in July 2016, examined evidence suggesting that Omar al-Bayoumi, a Saudi national in San Diego who had helped two of the eventual hijackers find housing and open bank accounts, may have had connections to Saudi intelligence. The pages also described the financial support that the Saudi government, and specifically the Saudi embassy in Washington, may have provided to persons connected to Al-Qaeda.
Saudi Arabia’s official position has been that neither the government nor any official provided support to the September 11 operation, and that the hijackers acted against the Saudi government’s wishes and contrary to Saudi values. The FBI’s investigation, whose conclusions were partially reflected in the 28 pages, reached more ambiguous conclusions about individual Saudi officials’ knowledge and potential support. The Justice Against Sponsors of Terrorism Act (JASTA), passed by Congress in 2016 over Obama’s veto, allowed families of September 11 victims to sue Saudi Arabia in American courts, producing the ongoing litigation that has provided additional motivation for the Saudi government to contest the historical record.
The broader Saudi-American relationship after September 11 was one of managed tension: both countries needed the relationship for strategic reasons, both had reasons to avoid full public accounting of the Saudi dimensions of the attacks, and the subsequent American decisions to invade Iraq and overthrow Saddam Hussein (who was a Saudi adversary) partly reflected the strategic accommodation that the Saudi-American relationship required.
Q: How did the attacks affect New York City and what is the memorial like?
New York City’s experience of September 11 was simultaneously the most direct experience of any American city, as the attacks’ primary physical location, and a transformative event that reshaped the city’s relationship with its own geography, with the firefighters and police who died, and with the national politics that the attacks generated.
The immediate aftermath in New York was a crisis of survival and rescue that involved approximately 300 hospitals, clinics, and medical centres treating the injured; approximately 100,000 volunteers who came to help with rescue and cleanup operations; and the FDNY and NYPD grief that the loss of 343 firefighters and 72 police officers represented for those communities. The Pile, as the rescue workers called the World Trade Center site, was worked continuously for months as hopes of finding survivors gave way to the systematic recovery of remains.
The air quality in lower Manhattan in the weeks following the attacks was a public health emergency that was not fully acknowledged at the time. The dust from the collapse of the towers, which contained asbestos, lead, mercury, and numerous other toxic substances, was inhaled by rescue workers and nearby residents whose subsequent health consequences the federal government was slow to acknowledge and reluctant to fund treatment for. The September 11th Victim Compensation Fund, which was eventually established and expanded by the Zadroga Act of 2010, addressed some of these health consequences, though advocates including first responders and comedian Jon Stewart continued to press for adequate funding for years after the initial legislation.
The 9/11 Memorial’s design, featuring two vast reflecting pools in the footprints of the original towers with the names of all 2,977 victims inscribed around their edges, communicates both the scale of the loss, with nearly 3,000 names inscribed in the stone, and the specific quality of individual remembrance that each name represents. The museum beneath the memorial, accessible through a building constructed at the site, houses recovered artefacts, extensive testimony, and historical documentation that places the attacks in the context of Al-Qaeda’s history and subsequent consequences.
Q: What was the role of flight passengers and crew and how did they respond?
The response of the passengers and crew on the four hijacked aircraft varied by circumstance and information, and the difference between the responses on the three aircraft that struck their targets and Flight 93, whose passengers fought back, reflects the role of information in producing the courage that resistance required.
The flight attendants and pilots on all four aircraft attempted to communicate with airline dispatchers and air traffic controllers through the limited means available. Betty Ong, a flight attendant on Flight 11, made a twenty-minute phone call to an American Airlines reservations agent describing the hijacking in progress, providing information that documented the hijacking in real time and that was used by the 9/11 Commission to reconstruct the timeline. Amy Sweeney, another Flight 11 attendant, made a separate call describing seat assignments that helped identify the hijackers.
The passengers on Flight 93 knew, through phone calls to family and from a GTE phone operator, that two other aircraft had already struck the World Trade Center. This information, unavailable to passengers on the earlier flights, gave them the knowledge that changed the calculation: they understood that the standard hijacking protocol of compliance to enable negotiation did not apply, and that their aircraft was being flown toward a target they could not identify.
The decision to attempt to overpower the hijackers was taken collectively, through the passenger calls and through the conversation that Todd Beamer had with a GTE phone operator before the attempt began. Beamer’s phrase “Let’s roll,” heard on the cockpit voice recorder, became one of the most quoted expressions of individual courage from September 11. The passengers’ assault on the cockpit was sufficient to prevent the hijackers from successfully attacking their intended target, even though none of the passengers survived.
Q: What was the impact on American foreign policy beyond Afghanistan and Iraq?
September 11’s impact on American foreign policy extended well beyond the specific military operations in Afghanistan and Iraq to reshape the entire framework within which American power was understood and applied.
The Bush Doctrine, articulated in the June 2002 West Point speech and formalised in the National Security Strategy of September 2002, represented the most significant reformulation of American foreign policy since the Cold War’s containment doctrine. Its key elements included the pre-emption principle, the assertion that the United States had the right to act militarily against potential threats before they materialised; the commitment to maintaining American military supremacy globally; and the democracy promotion agenda that held that spreading democracy would address the underlying conditions that produced terrorism.
The pre-emption principle was the most consequential element, as it provided the intellectual framework for the Iraq invasion and for subsequent assertions of American military authority that did not require the traditional international law requirements of imminent threat or UN authorisation. The Iraq War’s consequences severely damaged the pre-emption doctrine’s credibility, as the failure to find the weapons of mass destruction that provided its immediate justification demonstrated that pre-emptive action based on uncertain intelligence could produce catastrophic outcomes.
American relationships with Pakistan were permanently complicated by September 11. Pakistan was both essential to the Afghanistan operation, providing over-flight rights, basing, and intelligence cooperation, and simultaneously the country whose intelligence services had created the Taliban and retained relationships with its leadership. The specific tension between American dependence on Pakistani cooperation and Pakistani tolerance or support for the Taliban and Al-Qaeda-affiliated groups produced the most dysfunctional major bilateral relationship of the War on Terror period, culminating in the raid that killed bin Laden in a Pakistani military city without informing Pakistani authorities.
Relations with other Muslim-majority countries were also affected. The American drone strike programme, which conducted strikes in Pakistan, Yemen, Somalia, and other countries without their formal consent or sometimes without informing their governments, represented the extension of the post-September 11 claim to act unilaterally against terrorism that domestic legal frameworks in those countries and international law applied in complicated ways. The specific human costs of the drone programme, which killed significant numbers of civilians alongside its intended targets, generated the anti-American sentiment in the affected communities that the War on Terror’s architects had not adequately anticipated.
Q: How did September 11 affect privacy, surveillance, and digital rights?
September 11’s impact on privacy, surveillance, and digital rights produced the most significant transformation of the relationship between citizens and surveillance states since the Cold War, with consequences that are still being negotiated in courts, legislatures, and public debate.
The NSA’s post-September 11 expansion of signals intelligence collection, authorised under the President’s Surveillance Programme that Bush approved in October 2001, involved the collection of internet communications, telephone metadata, and financial transactions at a scale that went beyond what the Foreign Intelligence Surveillance Act of 1978 had been designed to authorise. The programme’s existence was initially classified; its legal basis was provided through secret opinions of the Office of Legal Counsel and the Foreign Intelligence Surveillance Court that created a parallel legal framework not available to public scrutiny.
Edward Snowden’s 2013 disclosure of NSA programmes including PRISM (which collected internet communications data from major technology companies), the bulk collection of telephone metadata under Section 215 of the PATRIOT Act, and the XKeyscore programme (which enabled searching of nearly everything that internet users do online), revealed the full scale of the post-September 11 surveillance expansion to the public and to much of Congress, which had not been fully informed about the programmes it had authorised. The disclosures produced the Freedom Act of 2015, which ended the bulk collection of telephone metadata under its specific Section 215 authority while preserving most other surveillance capabilities.
The disclosure also revealed the extent to which American surveillance programmes had been used against allied governments, including the personal communications of German Chancellor Angela Merkel, producing diplomatic friction that the Obama administration managed with varying degrees of success. The revelation that surveillance had extended from the terrorism targets that the post-September 11 expansion was justified to address, to foreign government leaders and to mass collection of communications by people with no terrorism connection, demonstrated that the emergency authorities claimed after September 11 had expanded beyond their original justification.
Q: How has the memory and meaning of September 11 been contested?
The memory and meaning of September 11 have been contested from the beginning, as the attacks’ scale and political consequences made them the subject of competing interpretations that reflect both genuine disagreements about causation and responsibility and the political interests that different parties have in shaping how the attacks are understood.
The conspiracy theories about September 11, which have attracted significant audiences in the United States and globally, represent the most extreme form of this contestation. The “9/11 Truth” movement’s claim that the attacks were an inside job, perpetrated by or with the knowledge of the American government, has been thoroughly investigated and thoroughly discredited by independent engineering analysis, extensive documentary evidence, and the implausibility of the secrecy that such a conspiracy would have required. But the movement’s persistence, and its appeal to people who distrust official accounts of politically significant events, reflects a broader crisis of epistemic authority that September 11 contributed to and that subsequent events have amplified.
More legitimate forms of historical contestation concern the specific intelligence failures that allowed the attacks to succeed, the decisions made in the aftermath that produced the Iraq War and the torture programme, and the appropriate lessons for American foreign policy from the War on Terror’s mixed record. These debates, conducted in congressional investigations, academic analysis, journalistic accounts, and political discourse, reflect the genuine uncertainty about some aspects of the events and the genuine disagreement about how the policy responses should be assessed.
The international dimension of September 11’s remembered meaning differs substantially from the American domestic narrative. In much of the Muslim world, the attacks are understood in the context of the subsequent American military operations that killed far more people than the attacks themselves, and the question of which events caused greater suffering is answered differently by people whose communities experienced the Iraq War or Afghanistan than by people whose communities experienced September 11. Whether this different contextualisation is a legitimate moral calculation or an evasion of the evil of the September 11 attacks is itself a contested question that different moral frameworks answer differently.
Q: What was the specific experience of first responders and what happened to them in the long term?
The first responders who arrived at the World Trade Center on September 11 and who worked on the rescue and recovery operation in the subsequent months experienced both the immediate trauma of witnessing mass death and the long-term health consequences of extended exposure to the toxic dust that the towers’ collapse had produced.
The immediate experience of the firefighters, police, and emergency medical personnel who responded to the towers was one of operating in conditions that no training had fully prepared them for. The collapse of the first tower (South) was unexpected; many firefighters were still inside the North Tower when it collapsed. The decision to enter buildings that were burning from aircraft impacts, and the specific courage required to continue ascending the stairwells as thousands of occupants descended, reflects the professional commitment that killed 343 firefighters.
The health consequences of the long-term ground zero exposure affected tens of thousands of rescue and recovery workers, cleanup crews, and lower Manhattan residents. The dust from the towers’ collapse contained asbestos fibres, glass shards, heavy metals, and combustion products from the buildings’ contents that produced increased rates of respiratory disease, multiple cancers including mesothelioma and rare blood cancers, and other conditions that the toxic mixture was associated with. The government’s initial response was inadequate: EPA administrator Christine Todd Whitman’s announcement within days of the attacks that the air quality in lower Manhattan was safe for return was subsequently determined to be based on incomplete testing and was driven partly by the desire to reopen lower Manhattan’s financial district rather than by accurate health assessment.
The Zadroga Act, named after NYPD detective James Zadroga who died of respiratory disease attributed to his ground zero exposure, was finally signed in 2010 after years of legislative struggle that required sustained advocacy from first responders, their families, and eventually a determined public campaign by comedian Jon Stewart. The Act established the September 11th Victim Compensation Fund and the World Trade Center Health Programme, which provide medical monitoring and treatment for those with documented ground zero exposure. The Act’s initial five-year term required reauthorisation in 2015, producing another advocacy campaign before its permanent reauthorisation in 2019.
Q: What was the role of the media in shaping the September 11 narrative?
The media’s role in September 11 was both documentary and constitutive: the attacks were filmed and broadcast in real time, creating the shared national experience that made them a genuinely collective trauma, and the subsequent coverage shaped the political and cultural response in ways whose effects persisted for years.
The live broadcast of the second aircraft’s impact on the South Tower was witnessed by millions of people simultaneously, making it the most watched act of violence in human history at the time it occurred. The television networks that had been covering the North Tower fire as a possible accident became the conduit through which the country understood that what was happening was a deliberate attack, and the hours of coverage that followed, showing the towers burning, the Pentagon damaged, and eventually both towers collapsing, created the psychological foundation of the collective experience.
The subsequent months’ media coverage was characterised by both genuine journalism and the dynamic of a media environment that was simultaneously reporting on events of enormous significance and operating within the post-September 11 political atmosphere in which critical questioning of government claims could be characterised as unpatriotic. The media’s handling of the intelligence claims about Iraqi weapons of mass destruction, which were reported with less scepticism than the evidence warranted, is the most consequential example of journalism that failed to apply the critical scrutiny that its professional standards required.
The international media’s coverage differed in ways that American audiences found both disturbing and informative. Coverage from the Arab world, and particularly Al Jazeera’s broadcasting of Osama bin Laden’s post-September 11 statements, created the specific American concern about whether international media were providing platforms for terrorist messaging or providing information that audiences needed to understand the context of a global conflict. The relationship between American media institutions and their foreign counterparts, and the question of what obligations international journalism had in covering a conflict where one side was explicitly seeking to use media coverage for recruitment and radicalisation, remained contested throughout the War on Terror period.
Q: What does September 11 mean for the relationship between open society and security?
September 11 posed the most direct challenge to open democratic societies that the post-Cold War period had produced: a challenge whose source was not a state adversary that could be deterred and contained but a transnational non-state network whose operational cells could be embedded within the open society they were attacking, using its freedoms as instruments for conducting operations against it.
The paradox of the response was that addressing the threat required measures that in some respects resembled the restrictions that democratic societies contrasted themselves with: surveillance, detention without trial, restrictions on movement, and the specifically coercive interrogation practices that the torture debate addressed. The argument that the open society’s survival required its partial closure, at least temporarily and for the specific purpose of defeating the threat, was made by defenders of the post-September 11 security measures and contested by those who argued that surrendering the values that defined open society was a greater threat than the terrorism it was designed to address.
The resolution of this tension that the American political system has reached is uncomfortable and unstable. The security apparatus created after September 11 has been reformed but not dismantled; some of its more extreme manifestations, including Guantánamo and the torture programme, have been reduced or ended, but the surveillance expansion, the military commissions, and the broad interpretation of presidential authority in national security that September 11 generated have proved more durable than the emergency that justified them.
Whether the democratic societies that responded to September 11 with security measures have maintained adequate commitment to the values those measures were supposed to protect, or whether the trade-off that was accepted has proven sufficiently durable and sufficiently justified by the threat it addressed, is a question that the lessons history teaches from September 11 do not resolve cleanly. The attacks created real threats that required real responses; the responses created real costs that required real assessment; and the appropriate balance between the two is a question that open democratic societies must continually renegotiate rather than settling once and for all. Tracing the arc from Al-Qaeda’s formation through the September 11 attacks to the transformation of American policy and the geopolitical shifts of the following decade is to follow the event that more than any other defined the twenty-first century’s opening era, and to follow it honestly requires holding both the attacks’ genuine horror and the responses’ genuine failures simultaneously.
Q: What was the impact of September 11 on American politics and the two-party system?
September 11’s impact on American domestic politics was both immediate and lasting, producing first a period of unusual bipartisan unity and then the specific polarisation dynamic that the War on Terror’s divisive consequences amplified.
The immediate post-September 11 political atmosphere was characterised by exceptional bipartisan solidarity. The Congressional response to Bush’s September 20 address was one of the most sustained standing ovations in American history; the subsequent authorisation of military force against Al-Qaeda passed the Senate 98-0 and the House 420-1, with only Barbara Lee of California voting against. The PATRIOT Act passed with overwhelming majorities. The Department of Homeland Security’s creation was broadly supported. The bipartisan quality of this response reflected both genuine national unity and the political calculus that opposing security measures in the immediate aftermath would be electorally devastating.
This unity dissolved relatively quickly. The 2002 midterm elections, in which Republicans gained seats in a pattern contrary to the historical norm for the president’s party, reflected the political benefit that the national security focus gave to the administration. The 2004 election, conducted in the shadow of the Iraq War’s first year and the Abu Ghraib torture revelations, produced the most security-dominated presidential campaign in recent history, with the Swift Boat Veterans’ campaign against John Kerry’s Vietnam record and Kerry’s own attempt to demonstrate national security credentials both reflecting the centrality of the terrorism and military themes to the electoral contest.
The dynamic that September 11 introduced into American political culture, in which support for aggressive security measures became associated with patriotism and opposition became associated with weakness, created an asymmetric political incentive that Democrats struggled to navigate for years. The “can’t afford to be wrong” logic that Bush administration officials applied to decisions about Iraq and other security matters reflected a political calculation as much as a security assessment: the political cost of appearing insufficiently vigilant exceeded the political cost of excessive caution.
Q: What happened to the Al-Qaeda network after September 11?
Al-Qaeda’s evolution after September 11 reflected the impact of the sustained counter-terrorism pressure that the American-led campaign applied to the organisation, which destroyed its Afghan sanctuary, killed or captured much of its original leadership, and forced the organisation to decentralise in ways that changed its character.
The Afghanistan campaign of 2001-2002 destroyed the training infrastructure that had prepared the September 11 hijackers and dozens of other operatives for attacks globally. The camps in which Al-Qaeda had trained thousands of fighters were destroyed; the Taliban government that had provided sanctuary was overthrown. Bin Laden and Zawahiri escaped into the Pakistani tribal areas, where they remained for years under a combination of tribal protection and ISI tolerance. Khalid Sheikh Mohammed was captured in Pakistan in 2003. Abu Musab al-Zarqawi, who had maintained a relatively separate organisation in Afghanistan, moved to Iraq and eventually created Al-Qaeda in Iraq.
The pressure on the original Al-Qaeda core organisation produced the development of the franchise model that defines contemporary jihadist terrorism. Al-Qaeda in Iraq (which evolved into ISIS), Al-Qaeda in the Arabian Peninsula (AQAP, based in Yemen), Al-Qaeda in the Maghreb (AQIM, operating across North Africa), and Al-Shabaab (in Somalia and East Africa) all developed as affiliated organisations that shared the Al-Qaeda name and broad ideology while operating independently of the central organisation’s direction. This decentralisation made the network simultaneously harder to destroy, because there was no single central target, and potentially less operationally effective than a centralised organisation, because the affiliates’ attacks were typically more local in scope than the September 11 planning had been.
The emergence of ISIS (the Islamic State of Iraq and Syria) from Al-Qaeda in Iraq represented the most significant development in the jihadist movement since September 11 itself. ISIS’s declaration of a caliphate in June 2014, its control of significant territory in Iraq and Syria, and its operational attacks in European cities between 2015 and 2017, represented a new form of jihadist threat that was simultaneously the most state-like and the most locally embedded that the movement had produced. Its eventual territorial defeat in 2019 did not eliminate the network but forced it into a clandestine mode similar to what the original Al-Qaeda had adopted after September 11.
Q: What is the continuing significance of the September 11 attacks for our understanding of terrorism?
September 11’s continuing significance for the understanding of terrorism extends beyond its status as the deadliest terrorist attack in history to its role in generating the most sustained and most extensively documented scholarly, policy, and legal engagement with terrorism that has ever occurred.
The attacks produced a massive expansion of terrorism studies as an academic field, with universities establishing counter-terrorism programmes, think tanks devoting sustained analysis to the Al-Qaeda network and its successors, and government agencies funding research on radicalisation, foreign fighter recruitment, and deradicalisation in ways that had no precedent. The body of knowledge about jihadist terrorism that has been produced in the fifteen years since September 11 is substantially larger and more sophisticated than what existed before, even if much of it remains classified.
The legal frameworks for addressing terrorism, which September 11 forced governments to develop and which have been refined through fifteen years of litigation and legislative development, represent a significant institutional legacy. The development of international legal cooperation mechanisms for extradition, asset freezing, and intelligence sharing, the UN Security Council resolutions that established obligations for all member states to criminalise and prevent terrorism financing and support, and the domestic legal changes in dozens of countries that increased the authorities available to security services, all reflect the institutional response that September 11 catalysed.
The question of what causes terrorism, and what conditions reduce the recruitment and radicalisation that feed terrorist organisations, has received more sustained attention since September 11 than in any previous period. The emerging consensus, which is contested but broadly supported by the research, is that military counter-terrorism alone cannot address the conditions that produce terrorist recruitment, and that the combination of law enforcement, intelligence, counter-narrative, and socioeconomic development efforts is more effective than military force alone in reducing the terrorist threat over the long term. Whether governments have applied this consensus consistently is a different question, one whose answer requires assessing the decisions made in the aftermath of September 11 and their consequences for the populations who have borne their costs.
Q: How have the September 11 attacks influenced debates about torture and detention?
The September 11 attacks produced the most consequential American debate about torture and detention since the Second World War, as the emergency conditions of the War on Terror generated the authorisations for “enhanced interrogation techniques” that the Senate Intelligence Committee subsequently characterised as torture, and as the detention facility at Guantánamo Bay produced a sustained legal and moral confrontation with the treatment of prisoners held outside normal legal frameworks.
The CIA’s enhanced interrogation programme, which waterboarded Khalid Sheikh Mohammed 183 times and applied other stress techniques including sleep deprivation, confinement in small spaces, and physical violence to approximately 119 detainees, was authorised by the Justice Department’s Office of Legal Counsel under opinions written by John Yoo and Jay Bybee that defined “torture” so narrowly that almost all of the programme’s techniques fell outside the definition. The Senate Intelligence Committee’s report, released in December 2014, found that the programme had produced little or no intelligence that could not have been obtained through non-coercive means, and that CIA briefings to the White House and Congress about the programme’s effectiveness had been systematically inaccurate.
The legal framework within which the debate occurred reflected September 11’s distortion of established legal standards. The United States’ obligations under the UN Convention Against Torture and the Geneva Conventions, both of which the US had ratified, were interpreted by Justice Department lawyers in ways that domestic and international legal scholars generally regarded as indefensible. The argument that the United States was engaged in an “armed conflict” against Al-Qaeda that removed the Geneva Conventions’ protections for prisoners, and that the Convention Against Torture’s prohibition of “cruel, inhuman, or degrading treatment” did not apply to actions taken in service of national security, represented a reinterpretation of settled legal standards that the Obama administration eventually repudiated through executive order.
The Guantánamo detention facility, which at its peak held approximately 780 detainees and which had detained many without charge or trial for extended periods, became the most visible symbol of the post-September 11 legal framework’s departure from the standards that American democracy had historically claimed to embody. Obama’s executive order on his second day in office directing its closure was never fully implemented, as Congress repeatedly blocked the transfer of detainees to the United States for trial or continued detention. The facility remains open, with a small remaining population, as a persistent reminder of the institutional legacy that September 11 created and that the political system has found impossible to resolve.
Q: How did September 11 shape the relationship between the United States and Europe?
September 11 and its aftermath produced the most significant test of the transatlantic relationship since the Cold War’s end, demonstrating both the depth of European solidarity with the United States after the attacks and the profound divisions that the Iraq War’s decision produced within the alliance.
The immediate European response to September 11 was one of genuine solidarity and sympathy. Le Monde’s headline “Nous sommes tous Américains” (We are all Americans) captured the emotional resonance of the attacks for European audiences who recognised, in the targeting of civilian workers in buildings that were symbols of capitalist achievement, the indiscriminate violence of terrorism that European countries had experienced in different forms through the IRA, ETA, and other domestic movements. NATO’s Article 5 invocation, and the deployment of European forces to Afghanistan under ISAF (International Security Assistance Force), reflected the genuine alliance commitment to supporting the United States.
The Iraq War decision shattered this solidarity. France and Germany’s opposition to the invasion, expressed through their threatened Security Council vetoes and their public condemnation of the American case for war, produced the “Old Europe/New Europe” split that Defence Secretary Donald Rumsfeld articulated, and the bilateral American-French relationship reached its lowest point since de Gaulle’s 1966 withdrawal from NATO’s military command. The specific Anglo-American relationship, with Blair’s government joining the invasion despite massive public opposition in Britain, demonstrated both the depth of that bilateral relationship and its political costs: Blair’s legacy was permanently shaped by the Iraq War and the intelligence failures that underpinned it.
The subsequent decade’s terrorism attacks in European cities, including Madrid in 2004 and London in 2005, converted the theoretical solidarity of September 11 into direct experience, producing European counter-terrorism cooperation with American intelligence services that has been the War on Terror’s most practically valuable international dimension. The NSA surveillance revelations of 2013, which demonstrated that American signals intelligence collection had targeted European leaders and European civilian populations alongside counter-terrorism targets, severely complicated this cooperation and produced lasting tensions about the relationship between intelligence partnership and sovereignty.
Q: What are the most important books, films, and documentaries about September 11?
The documentary and narrative record of September 11 is one of the richest produced by any single historical event in the era of mass media, spanning the immediate photographic and video documentation through a substantial body of investigative journalism, memoir, and academic analysis.
The 9/11 Commission Report, published in 2004, is the most authoritative single account of the attacks and their immediate context. Its narrative sections, written with unusual literary skill by the commission’s staff director Philip Zelikow, trace the planning and execution of the attacks with a clarity and detail that no subsequent account has surpassed. The report’s accessibility and the absence of classified redactions made it available to the general public in ways that intelligence community analyses were not, and it remains the essential starting point for understanding what happened.
Lawrence Wright’s “The Looming Tower” (2006), winner of the Pulitzer Prize, traced the development of Al-Qaeda and the intelligence community failures that allowed September 11 to proceed, through the intertwined stories of FBI and CIA officials whose institutional rivalry contributed to the failure to prevent the attacks. Wright’s combination of granular reporting and narrative intelligence produced a book that is simultaneously the best account of Al-Qaeda’s development and a devastating portrait of American institutional failure.
The documentary film “United 93” (2006), directed by Paul Greengrass, provided the most emotionally rigorous cinematic treatment of the attacks through its reconstruction of the final flight, combining the factual record of the cockpit voice recorder and passenger phone calls with the dramatic discipline of showing rather than explaining. Its restraint in the face of material that invited sentimentality or heroism made it the most artistically honest of the numerous cinematic treatments of September 11.
The photographs of September 11, particularly those of the towers burning and collapsing and of the Falling Man, are the primary visual documents of the event and have been the subject of sustained critical analysis about the ethics of documenting catastrophic death and the relationship between documentary photography and emotional and political truth.
The Cold War context that preceded September 11, the Soviet-Afghan War that created Al-Qaeda’s organisational infrastructure, and the subsequent War on Terror that September 11 produced, are all parts of a connected narrative whose full meaning requires understanding the arc from the Cold War’s end through Al-Qaeda’s formation to the attacks and their aftermath.
Q: How did the attacks affect children and how has the next generation processed September 11?
The generation of children who watched September 11 on television in classrooms, or whose parents came home early from work, or who were old enough to understand what they were seeing but not old enough to contextualise it, has grown up with the attacks as the defining event of their political consciousness in ways that are only now becoming visible in research, cultural production, and political participation.
The immediate experience of children on September 11 was shaped by whether their own families were directly affected and by the age at which they encountered the events. Children old enough to process the visual imagery of the towers falling and young enough to not yet have the emotional regulation that adults deploy for managing traumatic content, were exposed to material whose psychological effects are still being measured. The specific educational challenge that September 11 posed for teachers across the country, of explaining to children what terrorism was and why it had happened while managing their own responses to the attacks, was addressed with varying degrees of skill and sensitivity.
The generation that came of age after September 11, whose earliest political memories are of the War on Terror and whose adulthood has been shaped by the security infrastructure and the wars that September 11 produced, understands the attacks through a combination of documented history, family and community memory, and the political debates about the War on Terror’s effectiveness and costs that have characterised the years since. Their political engagement with questions of surveillance, civil liberties, and military intervention reflects the world that September 11 created, even as the attacks themselves recede into the historical distance that reduces the emotional immediacy of a generation that did not experience them.
The memorialisation and education programmes that have developed around September 11, from the museum and memorial at Ground Zero to the educational programmes developed by the September 11 Memorial and Museum, reflect the effort to transmit the meaning of the attacks to generations who did not experience them directly. Whether this transmission succeeds in conveying both the human reality of the attacks and the complexity of their causes and consequences, without collapsing either into simple patriotic narrative or into abstraction, is the challenge that September 11 education faces in the decades to come.
Q: What is the current state of the War on Terror and how does September 11’s legacy continue?
The War on Terror that September 11 initiated has never formally ended, and the question of when and how it concludes, or whether it can conclude at all under the frameworks that were built to sustain it, is one of the most important unresolved questions in contemporary international security.
The military dimensions of the War on Terror have evolved substantially since 2001. The Afghanistan War, which began as the response to the Taliban’s shelter of Al-Qaeda and which lasted twenty years before the Biden administration’s August 2021 withdrawal, ended with the Taliban’s return to power and with the recognition that the nation-building ambitions that had expanded the original counter-terrorism mission had failed. The Iraq War, whose connection to September 11 was asserted but not demonstrated, produced a civil war, an occupation, the emergence of ISIS, and a continuing American military presence that has outlasted the original justification.
The counter-terrorism dimensions have been more successful but also more institutionally entrenched. The intelligence sharing mechanisms, the financial intelligence systems that track terrorist financing, the law enforcement cooperation across dozens of countries, and the disruption of numerous plots since 2001 all represent genuine achievements. Whether these achievements required the scale of the surveillance expansion, the costs of Guantánamo and the detention and interrogation controversies, and the strategic failures of the Iraq and Afghanistan wars, is a question whose answer depends on the counterfactual assessment of what would have happened without those choices.
The ideological dimension of the War on Terror, the question of whether the conditions that produce jihadist recruitment are being addressed, has received less sustained attention from governments focused on immediate operational threats. The research consensus that military action alone cannot address recruitment conditions, and that the socioeconomic, governance, and identity dimensions of radicalisation require non-military responses, has been applied unevenly in the countries most affected by terrorism. Where it has been applied, including in the counter-radicalisation programmes of several European countries and the community engagement programmes of American law enforcement, results have been mixed but broadly more positive than military action alone.
Twenty-five years after September 11, the attacks remain the defining event of early twenty-first century history and the foundation of a security architecture whose long-term relationship to democratic values remains contested. The lessons history teaches from September 11 about the limits of what security measures can provide, the importance of addressing underlying conditions rather than only immediate threats, and the enduring cost of allowing emergency measures to become permanent features of democratic governance, are among the most important that the century’s opening decades have produced for those who must manage the security challenges that follow. Whether Western democracies can maintain the values of openness and due process while addressing genuine threats from transnational terrorism, and whether the frameworks built after September 11 can be reformed to reflect both the security lessons and the civil liberties costs that two decades of experience have revealed, is the central political and legal challenge that September 11’s legacy continues to pose.
Q: How did September 11 affect immigration and border security policy?
September 11’s transformation of American immigration and border security policy was among the most lasting domestic consequences of the attacks, producing changes in visa processing, entry screening, and the relationship between immigration enforcement and counter-terrorism that have affected hundreds of millions of travellers and immigrants since 2001.
The attacks’ revelation that fifteen of the nineteen hijackers had entered the United States on legal visas, and that the immigration and border security system had no mechanism for identifying and monitoring individuals who had been identified by intelligence as potential threats, produced immediate and comprehensive changes. The creation of the Department of Homeland Security brought immigration enforcement under the same institutional umbrella as border security and transportation security, reflecting the assessment that immigration was no longer primarily a labour and family unification policy matter but a security matter.
The US-VISIT programme, which collected biometric data including fingerprints and photographs from non-citizen travellers entering the United States, was implemented beginning in 2004 and established the biometric screening infrastructure that subsequent programmes have built upon. The Electronic System for Travel Authorization (ESTA), which requires travellers from visa-waiver countries to obtain advance electronic authorisation before travelling, was established in 2007. The Secure Communities programme extended immigration enforcement cooperation between federal and local law enforcement in ways that previous administrations had avoided.
The broader cultural and political impact of September 11 on immigration debates was to make security arguments central to discussions that had previously been primarily economic and humanitarian. The argument that immigration needed to be controlled for security reasons, which September 11 had seemingly validated by demonstrating that legal entrants could conduct mass-casualty attacks, provided political cover for immigration restriction positions that would previously have required purely economic or cultural justifications. Whether the security improvements achieved through the post-September 11 immigration changes justified their costs in terms of reduced immigration, damaged international relationships, and the treatment of immigrants as presumptive security threats is a debate whose terms September 11 permanently altered.
