Many wondered what to do with the Pentagon after the war ended, as the common view was that the War Department would have no need for a building so large in peacetime. Some said it should be converted into a hospital, a university or headquarters for the Veterans Administration, but the Army had no intention of giving it up. In September 1947, Congress passed the National Security Act, ushering in the single biggest military reorganization in American history. The act created the National Military Establishment, split the Air Force from the Army, formally established the Joint Chiefs of Staff and created the Central Intelligence Agency and the National Security Council.
In the post-World War II era, the Pentagon’s role was shaped decisively by growing Cold War tensions, as the wartime alliance with the Soviet Union disintegrated into a fierce rivalry, fueled by the nuclear arms race and the growing number of U.S. security commitments around the world. To provide a strong center for the military establishment, President Harry Truman wanted the Navy, Army and Air Force all to be headquartered in the Pentagon. James V. Forrestal, the nation’s first secretary of defense, took on that monumental task. Though Forrestal would be remembered by many as the “godfather” of the national security state, the great strain of the job exacerbated his existing mental illness, and he soon exhibited unmistakable signs of decline. After Truman replaced him with Louis Johnson in January 1949, Forrestal suffered a nervous breakdown; four months later, he committed suicide.
Despite this inauspicious start, the defense establishment continued to solidify itself, especially after August 1949, when the Soviet Union exploded an atomic bomb in Siberia. On August 10, Truman signed law giving the secretary of defense total power over the armed forces and renaming the National Military Establishment the Department of Defense. On the heels of North Korea’s invasion of South Korea in June 1950, the Pentagon staff returned to wartime highs; it would eventually reach 33,000. By the time the Korean War ended, the building had become a tourist attraction, with people strolling its grounds and inner courtyard, and gawking at its massive size. It had also become an unmistakable symbol of America’s growing military dominance in the world, a development that was celebrated by many and feared by many more.