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. When the odds were judged “fanciful”, the original plan was abandoned. The code-name was used instead for a defensive scenario, in which the British were to defend against a Soviet drive towards the North Sea and the Atlantic following the withdrawal of the American forces from the continent.
The study became the first of Cold War-era contingency plans for war with the Soviet Union. Both plans were highly secret at the time of their creation and it was not until 1998 that they were made public
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.
The plan was taken by the British Chiefs of Staff Committee as militarily unfeasible due to a three-to-one superiority of Soviet land forces in Europe and the Middle East, where the conflict was projected to take place. The majority of any offensive operation would have been undertaken by American and British forces, as well as Polish forces and up to 100,000 German Wehrmacht soldiers. Any quick success would be due to surprise alone. If a quick success could not be obtained before the onset of winter, the assessment was that the Allies would be committed to a total war which would be protracted. In the report of 22 May 1945, an offensive operation was deemed “hazardous”.
Given the acute sensitivity of their draft proposal for what was termed Operation Unthinkable, security was at a premium. Needless to say, too, Stalin learned very quickly what was going on in the British camp.
One of the many spies he had in Whitehall swiftly conveyed to Moscow tidings of an instruction that had gone out from London to Field Marshal Bernard Montgomery, the senior British commander in Germany, urging him to stockpile captured German weapons for possible future use.
In the report the planners drew up for the PM, they were quick with their reservations, pointing out that the Russians could resort to the same tactics they had employed with such success against the Germans, giving ground amid the infinite spaces of the Soviet Union.
Ultimately, Churchill knew in his heart that the tyranny established by the Red Army could not be undone either through diplomacy or by force of arms. But he never doubted the malevolence of Soviet intentions in Eastern Europe, and indeed around the world, and in that regard he was ahead of his time.
In the years after the war, it became progressively apparent that the Western Allies would have to adopt the strongest possible defensive measures against further Soviet aggression in Europe.
The U.S. dropped an atomic bomb on Japanese town Nagasaki, on August 9, 1945 – the month before Churchill got inside knowledge at Potsdam that they had completed a successful test of the bomb emboldening him to bring Stalin to heel
In August 1946, the U.S. chiefs of staff became sufficiently fearful of conflict with the Russians to initiate military planning for such a contingency. In London, the ‘Unthinkable’ file was taken out and dusted down.
Though at no time was it ever deemed politically acceptable or militarily practicable to attempt to free Eastern Europe by force of arms, military preparations for a conflict with the Soviet Union became a staple of the Cold War.
NBF – If the US did not have nuclear weapons, Stalin probably would not have been deterred from taking the rest of Europe after WW2.
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