The September 11 Attacks
Learn about the September 11, 2001 attacks — the terrorist strikes that killed nearly 3,000 people and launched the War on Terror that reshaped global politics.
The terrorist attacks of September 11, 2001, were the most devastating assault on American soil since Pearl Harbor and one of the defining events of the 21st century. Nineteen hijackers from al-Qaeda crashed four commercial aircraft: two into the World Trade Center in New York, one into the Pentagon, and one into a field in Pennsylvania after passengers fought back. Nearly 3,000 people were killed.
The attacks were the culmination of al-Qaeda leader Osama bin Laden's war against the United States, rooted in grievances over American military presence in Saudi Arabia, US support for Israel, and what bin Laden portrayed as Western war against Islam. The attacks exploited the openness of American society and the blind spots of its intelligence agencies, which had failed to connect warnings about the plot.
The consequences reshaped global politics. The United States invaded Afghanistan to destroy al-Qaeda's sanctuary and later Iraq under disputed pretexts about weapons of mass destruction. The 'War on Terror' expanded to dozens of countries, authorized drone strikes, indefinite detention, and mass surveillance programs that tested civil liberties. The attacks also fueled Islamophobia, destabilized the Middle East, and consumed trillions of dollars. Two decades later, the debate continues over whether the response to 9/11 made the world safer or more dangerous.