The September 11, 2001 (9/11) attacks were orchestrated and executed by the Islamist extremist terrorist organization al-Qaeda. The mastermind behind the attacks was al-Qaeda leader Osama bin Laden. The operational planner and instigator was Khalid Sheikh Mohammed, who came up with the tactical innovation of using hijacked airplanes as weapons to attack key U.S. targets. Nineteen hijackers, organized into teams, carried out the attacks, with most of them being Saudi nationals affiliated with al-Qaeda. The attacks targeted the World Trade Center in New York City and the Pentagon, with a fourth plane crashing in Pennsylvania after passengers attempted to regain control. Osama bin Laden and al-Qaeda claimed responsibility for the attacks, which led to significant U.S. and global responses including the war in Afghanistan to dismantle al-Qaeda and capture bin Laden.
