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.
Hamburg cell
The Hamburg cell () or Hamburg terror cell () was, according to U.S. and German intelligence agencies, a group of radical Islamists based in Hamburg, Germany that included students who eventually came to be key operatives in the 9/11 attacks. Important members included Mohamed Atta, who led the four hijacking teams in 2001 and piloted American Airlines Flight 11; Ramzi bin al-Shibh, who conspired with the other three members but was unable to enter the United States; Marwan al-Shehhi, who piloted United Airlines Flight 175; and Ziad Jarrah, who piloted United Airlines Flight 93 and failed to hit a target in Washington, D.C. (claimed by Khalid Sheikh Mohammed to have been the Capitol). Other members included Said Bahaji, Zakariya Essabar, Mounir el-Motassadeq, and Abdelghani Mzoudi.