The US Atomic Energy Commission gave pregnant women and newborn children iodine-131 to study the effect of radioactive material on placenta and thyroids of newborns.

J. Robert Oppenheimer is accused of disloyalty and communist contacts. President Dwight Eisenhower suspends Oppenheimer’s security clearance, and in a full hearing the following year, Oppenheimer is not reinstated. While many scientists defended him, Edward Teller did not, claiming Oppenheimer delayed working on the hydrogen bomb. In 1958, an AEC review finds the proceedings to be "a primitive abuse of the judicial system."

In his final State of the Union address, President Truman declares nuclear war impossible for "rational men."

Soviet leader Joseph Stalin dies.

Scientists study the impact of a nuclear blast on a fabricated American city during the test Annie at the Nevada Test Site. The test is part of Operation Cue, a series of projects conducted by the Federal Civil Defense Administration to evaluate the effects of nuclear detonations on civilian communities.

Nikita Khrushchev becomes the first secretary of the Communist party.

Julius and Ethel Rosenberg, sentenced as atomic spies in 1951, are executed by the U.S. [see March 29, 1951]

In a Foreign Policy article, U.S. physicist Robert Oppenheimer calls for greater openness in the atomic policy debate.

Armistice is signed, ending the war in Korea.

General Edmundson leads "Operation Big Stick." The mission requires him to take twenty B-36s, armed with nuclear weapons, to Okinawa in Japan.

Soviet Premier Georgi Malenkov announces that the USSR possesses the hydrogen bomb. The development of the hydrogen bomb in the U.S. and the Soviet Union, is regarded as the start of the Cold War arms race.

The Soviet Union tests its first simple fusion bomb, Joe 4, at the Semipalatinsk test site. The test is based on Andrei Sakharov’s "Layer Cake."

Lawyer William L. Borden sends letter to FBI Director J. Edgar Hoover accusing Robert Oppenheimer [Oppenheimer Hearings] of being a Soviet spy.

President Dwight Eisenhower orders a "blank wall" be placed between Robert Oppenheimer [Oppenheimer Hearings] and atomic secrets.

President Dwight Eisenhower, in a United Nations address, proposes Atoms for Peace, a program to extend American aid to other countries for establishing nuclear reactors for peaceful research. Eisenhower calls for the nuclear weapons states to give part of their nuclear stockpiles to a United Nations-supervised "bank of fissionable materials" in an attempt to strip nuclear energy of "its military casing and adapt it to the arts of peace."

Nikita Khrushchev authorizes the execution of Lavrentiy Beria, the former head of the Soviet secret police and the Soviet bomb project.

Atomic Energy Commission sends a letter with charges to U.S. physicist Robert Oppenheimer [Oppenheimer Hearings].