Operation Unthinkable was a code-name of two related plans of a conflict between the Western Allies and the Soviet Union. Both were ordered by British Prime Minister Winston Churchill in 1945 and developed by the British Armed Forces' Joint Planning Staff at the end of World War II in Europe.
The first of the two assumed a surprise attack on the Soviet forces stationed in Germany in order to "impose the will of the Western Allies" on the Soviets and force Joseph Stalin to honour the agreements in regards to the future of Central Europe.
The Chiefs of Staff were concerned that given the enormous size of Soviet forces deployed in Europe at the end of the war, and the perception that the Soviet leader Joseph Stalin was unreliable, there existed a Soviet threat to Western Europe. The Soviet numerical superiority was roughly 4:1 in men and 2:1 in tanks at the end of hostilities in Europe.[...] The Soviet Union had yet to launch its attack on Japan, and so one assumption in the report was that the Soviet Union would instead ally with Japan if the Western Allies commenced hostilities.
The hypothetical date for the start of the Allied invasion of Soviet-held Europe was scheduled for 1 July 1945.[...] The plan assumed a surprise attack by up to 47 British and American divisions in the area of Dresden, in the middle of Soviet lines.[...] This represented almost a half of roughly 100 divisions (ca. 2.5 million men) available to the British, American and Canadian headquarters at that time.[...]