What is the purpose of the pentagon being built?

Answer 1

Prior to construction of the Pentagon in Arlington, Virginia, the Department of War was located in a building adjacent to the White House in what is now known as the Eisenhower Executive Office Building or the "Old Executive Office Building." As the Department of War was transformed into the Defense Department, the various military branches, which had office located all over Washington, DC, some even in temporary trailers, required a central location from which to coordinate the nation's various military operations. The design of the Pentagon allowed the complex to house all of the required personnel in one location in a minimum of space. The Pentagon houses more than 50,000 employees of the Defense Department within its five sided complex. In addition to having five sides, the Pentagon has a series of corridors or concentric rings that allow offices to be stacked horizontally rather than vertically, keeping the height of the building lower.

By placing the headquarters, planning, operations, personnel, and other various departments together in one location, the Pentagon allows the various functions of the military to better coordinate and share intelligence, planning, and operations and save on the costs of these functions rather than each branch having their own facilities and personnel.