The Soviet Union tested its first atomic bomb; America's nuclear monopoly was broken.

On the morning of August 29, 1949, at the Semipalatinsk Test Site in Kazakhstan, the Soviet Union detonated its first nuclear weapon, codenamed "RDS-1"—an explosion equivalent to approximately 22 kilotons of TNT, comparable to the bombs dropped by the United States on Hiroshima and Nagasaki.

This test, coming just four years after the atomic bombings of Japan, ended the nuclear monopoly of the United States and forged the "balance of terror" between the two superpowers—a balance that shaped the face of the Cold War and even determined the fate of the decades to follow.