Only five months earlier, the Soviet Union had test detonated their first nuclear bomb, and, soon after that, British and U.S. intelligence came to believe that a top-ranking scientist in the U.S. nuclear program was actually a spy for the Soviet Union.

The USA successfully detonated "Mike", the world's first hydrogen bomb, on the Elugelab Atoll in the Pacific Marshall Islands on November 1st, 1952.

The 10.4-megaton thermonuclear bomb instantly vaporized an entire island, leaving behind a crater over a mile wide. The explosion created a mushroom cloud that, within 90 seconds, was 57,000 feet high. It would eventually stabilize at 120,000 feet high. Half an hour later it stretched 60 miles across.

On November 22, 1955, the Soviet Union detonated its first hydrogen bomb.