The Atomic Technology of War:

The Atomic Technology of War:

The spread of atomic weapons.

Scientists in several countries performed experiments in connection with nuclear reactors and fission weapons during World War II, but no country other than the United States carried its projects as far as separating uranium-235 or manufacturing plutonium-239.

The Axis powers

By the time the war began on Sept. 1, 1939, Germany had a special office for the military application of nuclear fission; chain-reaction experiments with uranium and carbon were being planned, and ways of separating the uranium isotopes were under study. Some measurements on carbon, later shown to be in error, led the physicist Werner Heisenberg to recommend that heavy water be used, instead, for the moderator. This dependence on scarce heavy water was a major reason the German experiments never reached a successful conclusion. The isotope separation studies were oriented toward low enrichments (about 1 percent uranium-235) for the chain reaction experiments; they never got past the laboratory apparatus stage, and several times these prototypes were destroyed in bombing attacks. As for the fission weapon itself, it was a rather distant goal, and practically nothing but "back-of-the-envelope" studies were done on it.

Like their counterparts elsewhere, Japanese scientists initiated research on an atomic bomb. In December 1940, Japan's leading scientist, Nishina Yoshio, undertook a small-scale research effort supported by the armed forces. It did not progress beyond the laboratory owing to lack of government support, resources, and uranium.

Great Britain.

The British weapon project started informally, as in the United States,among university physicists. In April 1940 a short paper by Otto Frisch and Rudolf Peierls, expanding on the idea of critical mass, estimated that a superweapon could be built using several pounds of pure uranium-235 and that this amount of material might be obtainable from a chain of diffusion tubes. This three-page memorandum was the first report to foretell with scientific conviction the practical possibility of making a bomb and the horrors it would bring. A group of scientists known as the MAUD committee was set up in the Ministry of Aircraft Production in April 1940 to decide if a uranium bomb could be made. The committee approved a report on July 15, 1941, concluding that the scheme for a uranium bomb was practicable, that work should continue on the highest priority, and that collaboration with the Americans should be continued and expanded. As the war took its toll on the economy, the British position evolved through 1942 and 1943 to one of full support for the American project with the realization that Britain's major effort would come after the war. While the British program was sharply reduced at home, approximately 50 scientists and engineers went to the United States at the end of 1943 and during 1944 to work on various aspects of the Manhattan Project. The valuable knowledge and experience they acquired sped the development of the British bomb after 1945.

The formal postwar decision to manufacture a British atomic bomb was made by Prime Minister Clement Attlee's government during a meeting of the Defence Subcommittee of the Cabinet in early January 1947. The construction of a first reactor to produce fissile material and associated facilities had gotten under way the year before. William Penney, a member of the British team at Los Alamos during the war, was placed in charge of fabricating and testing the bomb, which was to be of a plutonium type similar to the one dropped on Nagasaki. That Britain was developing nuclear weapons was not made public until Prime Minister Winston Churchill announced on Feb. 17, 1952, plans to test the first British-made atomic bomb at the Monte Bello Islands off the northwest coast of Australia. There, on Oct. 3, 1952, the first British atomic weapons test, called Hurricane, was successfully conducted aboard the frigate HMS Plym. By early 1954 Royal Air Force Canberra bombers were armed with atomic bombs.

The SovietUnion.

In the decade before the war, Soviet physicists were actively engaged in nuclear and atomic research. By 1939 they had established that, once uranium has been fissioned, each nucleus emits neutrons and can therefore, at least in theory, begin a chain reaction. The following year, physicists concluded that such a chain reaction could be ignited in either natural uranium or its isotope, uranium-235, and that this reaction could be sustained and controlled with a moderator such as heavy water. In June 1940 the Soviet Academy of Sciences established the Uranium Commission to study the "uranium problem."

In February 1939, news had reached Soviet physicists of the discovery of nuclear fission in the West. The military implications of such a discovery were immediately apparent, but Soviet research was brought to a halt by the German invasion in June 1941. In early 1942 the physicist Georgy N. Flerov noticed that articles on nuclear fission were no longer appearing in western journals; this indicated that research on the subject had become secret. In response, Flerov wrote to, among others, Premier Joseph Stalin, insisting that "we must build the uranium bomb without delay." In 1939 Stalin ordered the commencement of a research project under the supervision of Igor V. Kurchatov, who had been director of the nuclear physics laboratory at the Physico-Technical Institute in Leningrad. Kurchatov initiated work on three fronts: achieving a chain reaction in a uranium pile, designing both uranium-235 and plutonium bombs, and separating isotopes from these materials.

By the end of 1944, 100 scientists were working under Kurchatov, and by the time of the Potsdam Conference, which brought the Allied leaders together the day after the Trinity test, the project on the atomic bomb was seriously under way. During one session at the conference, Truman remarked to Stalin that the United States had built a "new weapon of unusual destructive force." Stalin replied that he would like to see the United States make "good use of it against the Japanese."

Upon his return from Potsdam, Stalin ordered that work on the fission bomb proceed at a faster pace. On Aug. 7, 1945, the day after the bombing of Hiroshima, he placed Lavrenty