Soviet physicist, Andrei Sakharov, starts working at the secret Arzamas-16 nuclear weapons laboratory.

Plutonium separation begins at the Mayak complex near Chelyabinsk, dumping highly radioactive waste into the Techa river. Radioactivity from the Techa river is discovered in the Arctic as early as 1951.

General Curtis LeMay’s first nuclear war plan for the Strategic Air Command envisions attacks on 70 Soviet cities with 133 bombs.

The North Atlantic Treaty establishes NATO, a military alliance aimed at protecting Western nations from the Soviet bloc.

The Communist party wins elections in Hungary.

Physicist Edward Teller rejoins the staff at Los Alamos, New Mexico.

UN Atomic Energy Commission suspends its meetings because of irreconcilable differences between the U.S. and USSR.

The Soviet Union detonates its first atomic bomb, Joe 1 (10-20 kilotons), at Semipalatinsk in Kazakhstan.

A U.S. weather plane, flying off the coast of Siberia, picks up evidence of radioactivity.

President Truman announces the explosion of the first Soviet atomic bomb.

The U.S. government expands the production of uranium and plutonium.

The General Advisory Committee to the U.S. Atomic Energy Commission argues against a crash program to develop the hydrogen bomb.

Atomic Energy Commissioner Lewis Strauss urges President Truman, in a letter, to give the highest priority to development of the hydrogen bomb.

The United States Atomic Energy Commission begins "Operation Green Run." The operation consisted of releasing 8,000 curies of radiation on three small towns near the Hanford testing site in Washington.

The Hanford Nuclear Plant releases three tons of irradiated uranium fuel in an experiment called Green Run, aimed at duplicating pollution from a Soviet reactor. The experiment places more than 7,800 curies of radioactive iodine-131, known to cause thyroid cancer in humans, into the environment. This classified atomic intelligence experiment was not disclosed for almost four decades.