The 11th of September 2024 marks the 23rd anniversary of 9/11 attacks on the US.
On Tuesday, 11 September 2001, suicide attackers seized US passenger jets and crashed them into two New York skyscrapers, killing thousands of people.
The attack remains one of the most traumatic events of the century, not only for Americans but also for the world.

On the morning of 11 September 2001, 19 terrorists from the Islamist extreme group al Qaeda hijacked four commercial aircraft and crashed two of them into the North and South Towers of the World Trade Center complex in New York City. A third plane crashed into the Pentagon in Arlington, Virginia. After learning about the other attacks, passengers on the fourth hijacked plane, Flight 93, fought back, and the plane was crashed into an empty field in western Pennsylvania about 20 minutes by air from Washington, D.C. The Twin Towers ultimately collapsed, due to the damage from the impacts and subsequent fires. Nearly 3,000 people were killed from 93 different countries. Most of the fatalities were from the attacks on the World Trade Center. The Pentagon lost 184 civilians and servicemembers and 40 people were killed on Flight 93. It was the worst attack on American soil since the Japanese attacked Pearl Harbor in 1941.
After the Taliban refused to turn over the mastermind of the attacks, Osama Bin Laden, Operation Enduring Freedom officially began 7 October 2001 with American and British bombing strikes against al Qaeda and Taliban forces in Afghanistan. Initially, the Taliban was removed from power and al Qaeda was seriously crippled, but allied forces continually dealt with a stubborn Taliban insurgency, infrastructure rebuilding, and corruption among the Afghan National Army, Afghan National Police, and Afghan Border Police. Bin Laden would go into hiding for nearly 10 years.
On 2 May 2011, U.S. Navy SEALs launched a nighttime raid on Bin Laden’s compound in Abbottabad, Pakistan, killing the al Qaeda leader. Operation Enduring Freedom officially ended 28 December 2014, although coalition forces remained on the ground to assist with training Afghan security forces. American troops departed Afghanistan in August 2021.
The key operational planner of the September 11 attacks was Khalid Sheikh Mohammed (often referred to simply as “KSM” in the later 9/11 Commission Report and in the media), who had spent his youth in Kuwait. Khalid Sheikh Mohammed became active in the Muslim Brotherhood, which he joined at age 16, and then went to the United States to attend college, receiving a degree from North Carolina Agricultural and Technical State University in 1986. Afterward he traveled to Pakistan and then Afghanistan to wage jihad against the Soviet Union, which had launched an invasion against Afghanistan in 1979.
According to Yosri Fouda, a journalist at the Arabic-language cable television channel Al Jazeera who interviewed him in 2002, Khalid Sheikh Mohammed planned to blow up some dozen American planes in Asia during the mid-1990s, a plot (known as “Bojinka”) that failed, “but the dream of Khalid Sheikh Mohammed never faded. And I think by putting his hand in the hands of bin Laden, he realized that now he stood a chance of bringing about his long awaited dream.”
In 1996 Khalid Sheikh Mohammed met bin Laden in Tora Bora, Afghanistan. The 9-11 Commission (formally the National Commission on Terrorist Attacks Upon the United States), set up in 2002 by U.S. Pres. George W. Bush and the U.S. Congress to investigate the attacks of 2001, explained that it was then that Khalid Sheikh Mohammed “presented a proposal for an operation that would involve training pilots who would crash planes into buildings in the United States.” Khalid Sheikh Mohammed dreamed up the tactical innovation of using hijacked planes to attack the United States, al-Qaeda provided the personnel, money, and logistical support to execute the operation, and bin Laden wove the attacks on New York and Washington into a larger strategic framework of attacking the “far enemy”—the United States—in order to bring about regime change across the Middle East.
The September 11 plot demonstrated that al-Qaeda was an organization of global reach. The plot played out across the globe with planning meetings in Malaysia, operatives taking flight lessons in the United States, coordination by plot leaders based in Hamburg, Germany, money transfers from Dubai, and recruitment of suicide operatives from countries around the Middle East—all activities that were ultimately overseen by al-Qaeda’s leaders in Afghanistan.
Key parts of the September 11 plot took shape in Hamburg. Four of the key pilots and planners in the “Hamburg cell” who would take operational control of the September 11 attacks, including the lead hijacker Mohammed Atta, had a chance meeting on a train in Germany in 1999 with an Islamist militant who struck up a conversation with them about fighting jihad in the Russian republic of Chechnya. The militant put the Hamburg cell in touch with an al-Qaeda operative living in Germany who explained that it was difficult to get to Chechnya at that time, because many travelers were being detained in Georgia. He recommended they go to Afghanistan instead.
Although Afghanistan was critical to the rise of al-Qaeda, it was the experience that some of the plotters acquired in the West that made them simultaneously more zealous and better equipped to carry out the attacks. Three of the four plotters who would pilot the hijacked planes on September 11 and one of the key planners, Ramzi Binalshibh, became more radical while living in Hamburg. Some combination of perceived or real discrimination, alienation, and homesickness seems to have turned them all in a more militant direction. Increasingly cutting themselves off from the outside world, they gradually radicalized each other, and eventually the friends decided to wage battle in bin Laden’s global jihad, setting off for Afghanistan in 1999 in search of al-Qaeda.
Atta and the other members of the Hamburg group arrived in Afghanistan in 1999 right at the moment that the September 11 plot was beginning to take shape. Bin Laden and his military commander Muhammad Atef realized that Atta and his fellow Western-educated jihadists were far better suited to lead the attacks on Washington and New York than the men they had already recruited, leading bin Laden to appoint Atta to head the operation.
The hijackers, most of whom were from Saudi Arabia, established themselves in the United States, many well in advance of the attacks. They traveled in small groups, and some of them received commercial flight training.
Throughout his stay in the United States, Atta kept Binalshibh updated on the plot’s progress via e-mail. To cloak his activities, Atta wrote the messages as if he were writing to his girlfriend “Jenny,” using innocuous code to inform Binalshibh that they were almost complete in their training and readiness for the attacks. Atta wrote in one message, “The first semester commences in three weeks…Nineteen certificates for private education and four exams.” The referenced 19 “certificates” were code that identified the 19 al-Qaeda hijackers, while the four “exams” identified the targets of the attacks.
In the early morning of August 29, 2001, Atta called Binalshibh and said he had a riddle that he was trying to solve: “Two sticks, a dash and a cake with a stick down—what is it?” After considering the question, Binalshibh realized that Atta was telling him that the attacks would occur in two weeks—the two sticks being the number 11 and the cake with a stick down a 9. Putting it together, it meant that the attacks would occur on 11-9, or 11 September (in most countries the day precedes the month in numeric dates, but in the United States the month precedes the day; hence, it was 9-11 in the United States). On September 5 Binalshibh left Germany for Pakistan. Once there he sent a messenger to Afghanistan to inform bin Laden about both the day of the attack and its scope.
One World Trade Center and the National September 11 Memorial and Museum
The physical and symbolic void left by the destruction of the Twin Towers was filled on November 3, 2014, with the opening of One World Trade Center, a 1,776-foot (541.3-metre) skyscraper, which instantly became a dramatic new landmark on the Manhattan skyline. Adjacent to One World Trade Center are the National September 11 Memorial and Museum (completed in 2011 and 2014, respectively). Within the 8-acre (3.2-hectare) memorial plaza, twin 1-acre (0.4-hectare) reflecting pools occupy the footprints of the Twin Towers. The pools feature the largest man-made waterfalls in North America and are edged by bronze panels inscribed with the names of the victims of the September 11 attacks as well as the names of the six people who died as a result of the truck bombing of the World Trade Center in February 1993. Among more than 400 trees in the grove that surrounds the pools is the “Survivor Tree,” a Callery pear tree that was discovered badly damaged at Ground Zero, removed and nursed back to health, and then returned to the site in 2010. The memorial and plaza were designed by architects Michael Arad and Peter Walker, winners of a design competition that featured 5,201 submissions from 63 countries.
The museum includes a glass-encased pavilion with an atrium that features two 80-foot (24-metre) trident-shaped steel columns that were part of the facade of the North Tower. The museum’s Memorial Hall is adorned with 2,983 tiles (representing the victims of the September 2001 and February 1993 attacks), each one a blue watercolour with which artist Spencer Finch attempted to capture the colour of the sky on the day of the September 11 attacks. At the centre of the tiles is a quote from Virgil’s Aeneid:
No day shall erase you from the memory of time
The museum’s Foundation Hall is a high-ceilinged, nearly 15,000-square-foot (1,400-square-metre) room that encompasses part of a surviving retaining wall of the World Trade Center and displays the “Last Column,” a 36-foot (11-metre) steel beam to which workers and others attached messages and posters during Ground Zero cleanup operations. The international impact of the September 11 attacks is demonstrated along the ramp that descends into the museum by a multimedia exhibit featuring recorded reminiscences by people from 43 countries in 28 languages.
The hunt for bin Laden
In September 2001 President Bush announced that he wanted Osama bin Laden captured—dead or alive—and a $25 million bounty was eventually issued for information leading to the killing or capture of bin Laden. Bin Laden evaded capture, however, including in December 2001, when he was tracked by U.S. forces to the mountains of Tora Bora in eastern Afghanistan. Bin Laden’s trail subsequently went cold, and he was thought to be living somewhere in the Afghanistan-Pakistan tribal regions.
U.S. intelligence eventually located him in Pakistan, living in the garrison city of Abbottabad, and in the early morning hours of May 2, 2011, on orders from U.S. Pres. Barack Obama, a small team of U.S. Navy SEALs assaulted his compound and shot and killed the al-Qaeda leader.