Britannica
Sources used in this answer
When did the Soviet Union test its first atomic bomb?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
The Soviet Union conducted its first successful test of an atomic bomb on August 29, 1949.12
Known in the West as Joe-1, the device was a plutonium-based weapon with a yield of approximately 20 kilotons. The successful detonation marked the end of the United States' nuclear monopoly, a pivotal moment that intensified the arms race and fundamentally altered the strategic landscape of the Cold War.132