Operation Unthinkable: Churchill’s Secret Plan for War Against the Soviet Union

Operation Unthinkable was a secret military plan developed in 1945 by British Prime Minister Winston Churchill. The plan explored the possibility of a surprise military attack against the Soviet Union, one of the more intriguing yet lesser-known aspects of the post-World War II era. While it was never implemented, Operation Unthinkable provides insight into the geopolitical tensions emerging before the war officially ended, foreshadowing the Cold War.

Background: The Shift from Alliance to Tension

During World War II, the Western Allies (the United States, the United Kingdom, and their partners) and the Soviet Union formed an uneasy alliance against Nazi Germany. Despite ideological differences, the necessity of defeating a common enemy brought them together. However, as the war neared its conclusion, tensions between the Western Allies and the Soviet Union began to surface, particularly over the future of Eastern Europe.

By 1944–1945, Churchill grew increasingly concerned about Soviet leader Joseph Stalin’s ambitions. The Soviet Union had liberated much of Eastern Europe from Nazi control. Still, instead of allowing these nations to pursue their own paths, Stalin installed pro-Soviet governments, effectively expanding Soviet…