The United States detonates the world's first atomic device at the Trinity test site near Alamogordo, New Mexico.
On August 6, the U.S. B-29 bomber drops a "Little Boy" uranium gun-type bomb with an approximate yield of 15 kilotons on Hiroshima. On August 9, the U.S. drops a second, "Fat Man" plutonium implosion type bomb with an approximate yield of 21 kilotons on the city of Nagasaki. This was the first and only time nuclear weapons were used on civilians.
The UN General Assembly adopts its first resolution, which establishes an Atomic Energy Commission and calls for the “elimination from national armaments of atomic weapons and all other major weapons adaptable to mass destruction.”
At the first meeting of the UN Atomic Energy Commission, U.S. delegate Bernard Baruch presents a proposal to internationalize control of atomic energy. Based on the Acheson-Lilienthal Report, the plan lays the groundwork for the future nonproliferation regime, but is rejected by the Soviet Union as too advantageous to the United States. On December 20, the UN Atomic Energy Commission approves the Baruch plan calling for the creation of an international atomic development authority. In doing so, it rejects the Soviet plan which called for U.S. nuclear disarmament before any international agency is created.
On August 29, 1949, the USSR detonates its first nuclear explosive device, “RDS-1” (US designation Joe 1) (10-20 kilotons), a plutonium bomb of similar design to the U.S. Fat Man, at Semipalatinsk test site in Kazakhstan. The Soviet nuclear test marks the beginning of the nuclear arms race between the USSR and United States.
Argentina sets up its atomic energy agency and begins research on nuclear weapons.
The Soviet nuclear test marked the beginning of the nuclear arms race between the USSR and U.S.
In response to Argentina’s nuclear program, Brazil begins its long-term effort to develop nuclear weapons technology.
U.N. General Assembly resolution 502 (VI) establishes the U.N. Disarmament Commission to address questions regarding nuclear disarmament after the dissolution of the U.N. Atomic Energy Commission.
First British atomic bomb, "Hurricane," is tested at Monte Bello Islands, Australia, with a yield of 25 kilotons.
