The plan proposed a massive surprise attack scheduled for .

Operation Unthinkable was a top-secret British military contingency plan drafted in May 1945, just days after Nazi Germany's surrender. Conceived by Winston Churchill, the plan explored the possibility of a surprise Allied offensive against the Soviet Union to "impose upon Russia the will of the United States and the British Empire". The Core Objective

Churchill was deeply concerned by Joseph Stalin's expansion into Eastern Europe, particularly the Soviet occupation of Poland. The primary goal was to force a "square deal" for Poland and secure a withdrawal of the Red Army to its pre-war borders. Military Strategy and Forces