On September 11, 2001, 53 Army civilians (47 employees and six contractors) and 22 soldiers were among the 125 victims killed in the Pentagon in a terrorist attack when American Airlines Flight 77 commandeered by five Al-Qaeda hijackers slammed into the western side of the building, as part of the September 11 attacks. Lieutenant General Timothy Maude was the highest-ranking military official killed at the Pentagon, and the most senior U.S. Army officer killed by foreign action since the death of Lieutenant General Simon B. Buckner, Jr. on June 18, 1945, in the Battle of Okinawa during World War II.

How many victims were killed in the attack on the Pentagon?