The Al Qaeda-led terrorist attacks of September 11, 2001, were a series of coordinated suicide attacks carried out by the Islamist extremist group Al Qaeda against targets in the United States. These attacks included the hijacking of four commercial airplanes, resulting in the destruction of the Twin Towers of the World Trade Center in New York City and significant damage to the Pentagon in Arlington, Virginia. The events of 9/11 not only caused immense loss of life but also triggered profound changes in U.S. foreign policy and national security measures.