One of the most significant outcomes of World War II was the enormous momentum of militarization. Four years of global conflict—indeed, two world wars in a single generation—had left a powerful imprint. Neither the Soviet Union nor the United States ever fully demobilized. Troops from both nations remained encamped in the heart of Europe, while U.S. air and naval bases spread throughout the world. Although the Soviet Red Army was the world's largest ground force, the United States possessed a formidable two-ocean navy and the most powerful air force the world had ever seen. As the Soviet economy and society struggled to rebuild from the ruins of war, U.S. economic might laid the foundation for the emergence of an awesome military power.
Sole possession of the atomic bomb offered both real and symbolic evidence of U.S. military superiority. Some historians have argued that the United States dropped the two bombs on Japan as much to make an impression on the Soviets as to end the Pacific war. "Atomic diplomacy" did not work, however, as Stalin adopted a nonchalant stance toward the bomb and refused to adjust Soviet political aims in deference to the U.S. monopoly. While Washington had shared atomic information with Great Britain during the war, the Soviets were kept in the dark—or so Americans thought. In actuality, Soviet spies had penetrated the atomic research program and stolen the secrets of the atom. Talks on international control of atomic weapons quickly foundered and became another casualty of the Cold War.
Both sides cultivated their military prowess and vowed to defend their territory and spheres of influence. While the Soviets trumpeted the heroic defense of the motherland against the Nazis, the Americans reorganized their defense establishment, now housed in the sprawling new Pentagon building. Under the National Security Act (1947), Washington created a new Department of Defense and departments of Air Force and Marines to join the Army and the Navy, all four branches coordinated by a new phalanx of generals, the Joint Chiefs of Staff. The legislation also created the National Security Council to advise the president on global foreign policy and the Central Intelligence Agency to gather information and carry out covert operations.
The West took the lead in dividing Europe into hostile military alliances. In 1949, acting under a UN provision for collective security arrangements, the West promulgated the North Atlantic Treaty Organization (NATO), a military alliance aimed squarely at the Soviet Union. The actual threat of a Soviet military attack on western Europe was remote, yet memories of Nazi blitzkrieg and Pearl Harbor remained vivid. More to the point, however, NATO furthered the course of Western economic and political integration and created a market for perpetuating the profitable wartime collusion between science, government, and the defense industry. The successful Soviet atomic test in 1949 fueled the nuclear arms race, as both powers pushed ahead with development of hydrogen, or thermonuclear, weapons. From this point forward, the two superpowers each cultivated the power to destroy one another in an all-out war.