Origins and authorization
In July 1941 Brigadier General Brehon B. Somervell, chief of Army Construction, outlined a consolidated headquarters to end the War Department's sprawl across seventeen buildings. Secretary of War Henry L. Stimson approved the concept the same day; President Franklin D. Roosevelt and Congress released an initial $35 million within ten days.1
Architectural planning
Washington architect George Bergstrom and structural engineer David J. Witmer produced a five-sided plan in one week. The pentagonal footprint satisfied Roosevelt's demand for low height, preserved Mall sightlines, and exploited the irregular Hell's Bottom tract. Reinforced concrete substituted for scarce steel, five concentric office rings linked by ten radial corridors minimized walking distances, and height was capped at five stories to avoid elevators.2
Construction timeline
Ground broke at 04:00 on 1941-09-11 under Colonel Leslie R. Groves. Crews drove 41 492 piles, poured 410 000 yd³ of concrete, and employed up to 15 000 laborers on continuous shifts. First occupants arrived 1942-04-30; final inspection occurred 1943-01-15, four months early, at a total cost of $83 million (≈$1.4 billion 2023 dollars).3
Postwar role
The National Military Establishment (1947) and later Department of Defense (1949) adopted the building as command node for the Joint Chiefs of Staff, National Military Command Center, and combatant command liaisons. About 26 000 personnel operate inside the five rings today.
UAP research and analysis units
These cells coordinate with the Defense Counterintelligence and Security Agency for cleared contractor data and rely on the Defense Clandestine Service for foreign collection.4
Public engagement
Press releases in December 2017 addressing the FLIR-1, Gimbal, and GoFast videos, and the 2020 statement authenticating them, originated from Room 2E973. Congressional briefings that informed the 2023 National Defense Authorization Act were held in the Pentagon Briefing Room and secure video suites.
Cultural significance
Public statements on UAP videos in 2017 and 2020 originated from Pentagon press operations, cementing the building as focal node for disclosure debates.