History › Our time › Globalization
September 11 attacks
September 11, 2001· Event· Americas & Oceania
Well documentedSolid records, physical evidence or scientific consensus.
On September 11, 2001, al-Qaeda terrorists hijacked four US airliners, killing nearly 3,000 people in New York, Washington and Pennsylvania.
See it on the History map →What happened
Nineteen hijackers, 15 of them Saudi citizens, seized four planes. Two struck the World Trade Center's twin towers, which collapsed; one hit the Pentagon; the fourth crashed in a Pennsylvania field after passengers fought back. The attack was planned by al-Qaeda, led by Osama bin Laden from Afghanistan, where the Taliban sheltered him. It was the deadliest terrorist attack in history and destroyed the 16-acre World Trade Center complex, over 13 million square feet of offices.
Why it matters
It launched the US 'war on terror', wars in Afghanistan and Iraq, and lasting changes to airport security, surveillance and intelligence.
How we know
The 9/11 Commission Report (2004), cockpit and phone recordings, video, and bin Laden's own later statements claiming responsibility.
Still debated
Why warnings were missed, and whether any Saudi officials helped the hijackers, were investigated for years; released FBI files remain debated.
Inside this (1)
Connections (2)
▸September 11 attacks led to the Wars in Afghanistan and IraqWell documented
The connection
Within a month of 9/11 the US attacked Afghanistan, whose Taliban government sheltered al-Qaeda. The attacks also changed US thinking about threats, and the Bush administration argued Saddam Hussein might give banned weapons to terrorists. Iraq had no role in 9/11, but the 'war on terror' framed the 2003 invasion.
When and how
Afghanistan from October 7, 2001; Iraq from March 20, 2003; President George W. Bush, British prime minister Tony Blair and allies.
How we know
Congress's 2001 authorization of force, leaders' speeches, and the 9/11 Commission, which found no operational link between Iraq and al-Qaeda.
Debates and open questions
Whether the US would have invaded Iraq without 9/11, and how far the attacks served as a pretext, is debated.
▸September 11 attacks had roots in the Soviet–Afghan war of the Cold WarMostly agreed
The connection
In the 1980s the US, Saudi Arabia and Pakistan armed Afghan mujahideen (holy warriors) fighting the Soviet invasion. Thousands of foreign Muslim volunteers joined, including Osama bin Laden. He founded al-Qaeda from that network around 1988, and after the Soviets left, it turned against the US.
When and how
Afghanistan and Pakistan, 1979–1989; al-Qaeda founded in Peshawar, Pakistan, around 1988.
How sure are we?
Declassified CIA records, the 9/11 Commission and histories such as Steve Coll's Ghost Wars trace these roots.
Debates and open questions
Whether the CIA ever directly aided bin Laden is disputed; most evidence says US aid went to Afghan groups, not Arab volunteers.