On 11 September 2001, the United States suffered the deadliest terrorist attack in its history, an event that killed nearly 3,000 people, destroyed New York’s Twin Towers and changed the course of international politics for decades.
The September 11 attacks unfolded over less than two hours, but their consequences would reshape American foreign policy, global security, air travel and conflicts thousands of kilometres from the places that were attacked.
Images of aircraft striking the World Trade Center and of the towers collapsing became some of the defining images of the early 21st century.
Four aircraft hijacked
On the morning of 11 September, 19 al-Qaeda hijackers seized control of four commercial passenger aircraft flying from airports on the US East Coast.
At 8:46 local time, American Airlines Flight 11 struck the North Tower of the World Trade Center in New York City.
Initially, there was uncertainty over whether the crash had been a catastrophic accident. That ended 17 minutes later, when United Airlines Flight 175 struck the South Tower in front of television cameras broadcasting live around the world.
It was now clear that the United States was under attack.
A third aircraft, American Airlines Flight 77, crashed into the Pentagon, the headquarters of the US Department of Defense, outside Washington DC.
The fourth, United Airlines Flight 93, never reached its intended target.
Passengers and crew members, having learned through phone calls about the attacks elsewhere, attempted to regain control of the aircraft from the hijackers. It crashed into a field near Shanksville, Pennsylvania, killing everyone aboard.
Its intended target has never been definitively established, although investigators concluded that the US Capitol was the most likely target.
The Twin Towers fall
In New York, fires caused by the aircraft impacts spread through the upper floors of the World Trade Center towers as thousands of people attempted to escape.
Emergency services rushed towards the disaster as office workers and civilians moved in the opposite direction.
At 9:59, the South Tower collapsed.
Twenty-nine minutes later, at 10:28, the North Tower followed.
The collapse sent enormous clouds of dust and debris through Lower Manhattan and destroyed or severely damaged surrounding buildings.
Among those killed were hundreds of firefighters, police officers and other emergency personnel who had entered the complex to evacuate civilians and respond to the attacks.
Nearly 3,000 people from more than 90 countries were killed in New York, at the Pentagon and aboard the four aircraft.
The victims ranged from young children to elderly passengers, office workers, airline crews and first responders.
A world transformed
Responsibility for the September 11 attacks was attributed to al-Qaeda, the Islamist extremist organisation led by Osama bin Laden.
Less than a month later, the United States and its allies launched military operations in Afghanistan after the Taliban government refused US demands concerning al-Qaeda.
The intervention became America’s longest war.
The attacks also ushered in what became known as the “War on Terror”, dramatically expanding counterterrorism operations, intelligence gathering and security measures in the United States and around the world.
Airport security was transformed. Governments introduced new surveillance and counterterrorism powers, while intelligence agencies increasingly focused on preventing transnational terrorist attacks.
Two years after 9/11, the United States invaded Iraq. The George W Bush administration argued that Saddam Hussein’s government possessed weapons of mass destruction and presented Iraq within its wider post-9/11 security strategy, although Iraq was not responsible for the September 11 attacks. The weapons stockpiles cited before the invasion were not found.
The wars and political upheaval that followed would shape the Middle East, US foreign policy and international relations for years.
The hunt for Osama bin Laden
Bin Laden remained at large for almost a decade after the attacks.
On 2 May 2011, US special forces killed the al-Qaeda leader during a raid on a compound in Abbottabad, Pakistan.
The death of bin Laden closed one chapter of the response to 9/11, but the conflict that began in Afghanistan continued for another decade.
US forces completed their withdrawal from Afghanistan in August 2021, almost 20 years after the September 11 attacks prompted the initial intervention. The Taliban rapidly returned to power.
Remembering the victims
Today, the footprints of the Twin Towers form part of the National September 11 Memorial in New York.
Two large reflecting pools stand where the towers once stood, surrounded by the names of those killed in the 2001 attacks as well as the victims of the 1993 World Trade Center bombing.
Every year on 11 September, the names of the victims are read aloud during a remembrance ceremony.
Moments of silence mark the times when the aircraft struck the towers and Pentagon, when the towers fell and when Flight 93 crashed in Pennsylvania.
For the families of those killed, however, September 11 is not simply an event in history.
Thousands of survivors, first responders and people who worked or lived around Ground Zero have also suffered illnesses linked to exposure to toxic dust and debris in the aftermath of the attacks.
A defining moment of the 21st century
More than two decades later, the September 11 attacks remain a dividing line in modern history.
They altered how governments thought about terrorism, borders, intelligence and national security. They led to wars whose consequences are still debated and contributed to political changes extending far beyond the United States.
For a generation old enough to remember that Tuesday morning, the images remain immediate: smoke pouring from Manhattan, people fleeing through dust-covered streets, firefighters walking towards the towers and an altered New York skyline.
For younger generations, 9/11 is increasingly history rather than memory.
But every 11 September, the commemorations return attention to the individuals at the centre of an event whose geopolitical consequences became enormous: the passengers, office workers, emergency responders and families whose ordinary morning became one of the defining days of the modern era.
Also read: A tribute to four-legged 9/11 heroes
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