who did 9/11

The September 11 attacks (9/11) were carried out by 19 militants associated with the Islamic extremist group al-Qaeda. The key figures behind the attacks include Osama bin Laden, who was the mastermind, and Khalid Sheikh Mohammed, the principal operational planner. Mohammed devised the tactic of hijacking planes to crash into significant U.S. landmarks. Mohamed Atta was selected to lead the hijackers within the United States. Most hijackers were from Saudi Arabia, and they received commercial flight training to carry out the attacks. The four coordinated attacks involved hijacking four planes: two were flown into the Twin Towers of the World Trade Center in New York City, one into the Pentagon, and the fourth crashed in Pennsylvania after passengers resisted the hijackers. These attacks led to profound changes in U.S. domestic and foreign policies, including the global war on terror.