Donald Rumsfeld
The United States was attacked on September 11, 2001 by al Qaeda terrorists who hijacked commercial airliners and crashed them in coordinated strikes into both towers of the World Trade Center in Lower Manhattan, New York City and the Pentagon in Washington, D.C. The fourth plane crashed into a field in Shanksville, Pennsylvania, and its target was likely a prominent building in Washington, D.C., most probably either the Capitol Building or the White House. Within three hours of the start of the first hijacking and two hours after American Airlines Flight 11 struck the World Trade Center, Rumsfeld raised the defense condition signaling of the United States offensive readiness to DEFCON 3, the highest it had been since the Arab-Israeli war in 1973.
Hijackers in the September 11 attacks
The hijackers in the September 11 attacks were 19 men affiliated with al-Qaeda. 15 of the 19 were citizens of Saudi Arabia, and the others were from the United Arab Emirates (2), Egypt, and Lebanon. The hijackers were organized into four teams, each led by a pilot-trained hijacker with three or four "muscle hijackers," who were trained to help subdue the pilots, passengers, and crew.