The Pentagon

The Pentagon, completed in 1943, is the headquarters of the United States Department of Defense and one of the largest office buildings in the world. Its distinctive five-sided shape has become global shorthand for the American military establishment itself.

It was built with extraordinary speed during World War II to consolidate the War Department's scattered offices into a single command center as the United States mobilized for global war. Tens of thousands of people work within its five concentric rings and five floors, planning and directing the operations of the armed forces.

After the war it became the nerve center of the Cold War military — the permanent command post for a nation that now kept a vast standing force. "The Pentagon" came to mean not just a building but the defense bureaucracy and its leadership.

On September 11, 2001, the Pentagon was struck by a hijacked airliner in the terrorist attacks, killing 184 people there and scarring the symbol of American military might. Rebuilt within a year, it remains the working heart of the U.S. defense establishment.