History of nuclear weapons

The history of nuclear weapons traces their development, testing, deployment, spread, and political effects from the early twentieth century onward.

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Manhattan Project: The United States-led wartime program that developed the first nuclear weapons. Its laboratories and production sites turned nuclear fission into a weapon during World War II.
Gun-type fission weapon: A fission weapon design that rapidly joins subcritical masses of fissile material to create an explosive chain reaction. Little Boy used this comparatively simple design, which did not require a full-scale nuclear test beforehand.
J. Robert Oppenheimer: The theoretical physicist who directed the Los Alamos Laboratory during the Manhattan Project. His leadership linked wartime bomb design to later public disputes over nuclear policy.
Cold War: A prolonged geopolitical rivalry between the United States and the Soviet Union and their allies after World War II. The superpower rivalry drove the largest nuclear arms race and framed most nuclear crises.
Castle Bravo: A 1954 U.S. thermonuclear test in the Marshall Islands that produced an unexpectedly large radioactive fallout plume. Its fallout contaminated nearby islanders and the Japanese fishing vessel Daigo Fukuryū Maru.
Nuclear fission: A nuclear reaction in which a heavy atomic nucleus splits, releasing energy and neutrons. The discovery of controllable fission made a chain-reaction weapon physically conceivable.
Implosion-type nuclear weapon: A nuclear weapon design that compresses fissile material with conventional explosives to produce a supercritical state. The Trinity device and Fat Man used implosion, enabling efficient use of plutonium.
Harry S. Truman: The 33rd president of the United States, who authorized the atomic bombings of Japan. His administration made the decision to use nuclear weapons in August 1945.
Cuban Missile Crisis: A 1962 confrontation between the United States and the Soviet Union over Soviet nuclear missiles in Cuba. It brought the superpowers close to nuclear war and prompted changes in crisis communication.
Daigo Fukuryū Maru: A Japanese fishing boat exposed to radioactive fallout from the 1954 Castle Bravo nuclear test. The crew's exposure helped intensify public concern about atmospheric testing.