1940 | 1941 | 1942 | 1943 | 1944 | 1945 | 1946 | 1947 | 1948 | 1949

It was not until July 13, 1942, in the midst of World War II, that the United States began developing an atomic bomb. By December 2, a Manhattan Project team headed by Enrico Fermi produced the first artificial fission reaction at the University of Chicago. Three years after its inception, the Manhattan Project achieved its goal of developing an atomic weapon.

World War II ended in Europe on May 8, 1945, less than a month after the death of President Franklin Roosevelt, but plans for the development and use of atomic weapons continued.

At at 5:29 a.m. on July 16, 1945, the United States conducted the world's first nuclear test explosion at Alamogordo, New Mexico. The Nuclear Age was born, a product of the fear, violence, and suffering of World War II. J. Robert Oppenheimer, director of the Los Alamos Laboratory, recalled the following passage from the Bhagavad Gita upon witnessing the explosion: "I am become death, the shatterer of worlds"

Within a month, nuclear weapons were used to destroy the Japanese cities of Hiroshima and Nagasaki. When he received word of the bombing of Hiroshima, President Truman exclaimed, "This is the greatest day in history!"

On August 8, 1945, two days after the U.S. dropped an atomic bomb on Hiroshima, representatives of the U.S., United Kingdom, U.S.S.R., and France created an International Military Tribunal at Nuremberg to try Axis leaders for war crimes. Japan signed a surrender agreement on September 2, ending the war in the Pacific.

On October 24, 1945, the United Nations Charter entered into force and the new international organization was founded. Yet the good intentions of this new peacekeeping organization were threatened by the onset of the Cold War. At the first meeting of the Atomic Energy Commission, the U.S. delegate proposed a plan to internationalize control of atomic energy. The plan was rejected by the Soviet Union, which tested its first nuclear weapons in 1949, ending the U.S. monopoly.

By 1947 the Cold War was playing a major role in U.S. foreign policy. The National Security Act created the Central Intelligence Agency (CIA), and the Truman Doctrine proclaimed that the U.S. would assist any country threatened by Communist aggression.

The Cold War intensified in February 1948 when the Communists took over Czechoslovakia and the U.S.S.R. initiated the Berlin Blockade. That same year UN General Assembly adopted a Convention on the Prevention and Punishment of the Crime of Genocide and the Universal Declaration of Human Rights.

By 1949 Chinese Communist insurgents led by Mao Tse-tung took power. The North Atlantic Treaty was signed, creating NATO, and the Berlin Blockade came to an end. In August, 1949, the USSR detonated its first atomic bomb.

The 1940s was the most violent decade of the century, ending with some 54,000,000 persons killed in warfare. Sixty percent were civilians.

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