Operation Unthinkable was the name given to two related possible future war plans developed by theBritish Chiefs of Staff Committee against theSoviet Union during 1945. The plans were never implemented. The creation of the plans was ordered byBritish Prime MinisterWinston Churchill in May 1945 and developed by theBritish Armed Forces' Joint Planning Staff in May 1945 at theend of World War II in Europe.[1]
One plan assumed a surprise attack on theSoviet forces stationed inGermany to impose "the will of the United States and British Empire upon Russia".[2] "The will" was qualified as "a square deal forPoland", but added that "that does not necessarily limit the military commitment".[3] The assessment, signed by the Chief of Army Staff on 9 June 1945, concluded: "It would be beyond our power to win a quick but limited success and we would be committed to a protracted war against heavy odds".[2] The code name was now reused instead for a second plan, which was a defensive scenario by which the British were to defend against a Soviet drive towards theNorth Sea and theAtlantic Ocean after the withdrawal of theAmerican forces from the Continent.
The study became the firstCold War-eracontingency plan forwar against the USSR.[4] Both plans were top secret and were not made public until 1998,[5] although Soviet spyGuy Burgess had passed on details to Soviet intelligence at the time.[6]
The initial primary goal of the operation was declared as "to impose upon Russia the will of theUnited States and theBritish Empire. Even though 'the will' of these two countries may be defined as no more than a square deal forPoland, that does not necessarily limit the military commitment".[3] (TheSoviet Union is referred to asRussia throughout the document, ametonym that was common in theWest throughout theCold War.)
The chiefs of staff were concerned that both the enormous size of the Soviet forces deployed inEurope at the end of the war and the perception that Soviet PremierJoseph Stalin was unreliable caused a Soviet threat to exist in Allied-heldWestern Europe. The USSR had yet to launch itsattack on Japanese forces and so one of the assumptions in the report was that the Soviets would instead ally with Japan if the Western Allies commenced hostilities.
The hypothetical date for the start of the Allied invasion of Soviet-heldEastern Europe was scheduled for 1 July 1945, four days before theUnited Kingdom general election.[7] The plan assumed asurprise attack by as many as 47 British and Americandivisions in the area ofDresden, in the middle of Soviet lines.[7] That represented almost half of the approximately 100 divisions available to the British, American and Canadian headquarters at that time.[8]
The plan was considered by the BritishChiefs of Staff Committee as militarily unfeasible due to an anticipated 2.5:1 superiority in divisions of Soviet ground forces within Europe and theMiddle East by 1 July, when the conflict was projected to occur.[9] Most of the offensive operation would have been performed by American and British forces, as well asPolish forces and as many as 10 divisions of theGerman Army, remobilised from prisoner-of-war status. Any quick success would be caused by surprise alone. If a quick success could not be obtained before the beginning of winter, the assessment was that the Allies would be committed to a protractedtotal war. In the report of 22 May 1945, an offensive operation was deemed "hazardous".
The following table is based on Allied estimates at the time of the planning of Operation Unthinkable.
| Allied | Soviet | Ratio | |
|---|---|---|---|
| Infantry divisions[a] | 80 | 228 | 1 : 2.85 |
| Armored divisions[b] | 23 | 36 | 1 : 1.57 |
| Tactical aircraft | 6,048[c] | 11,802 | 1 : 1.95 |
| Strategic aircraft | 2,750[d] | 960 | 2.86 : 1 |
In response to an instruction by Churchill of 10 June 1945, a follow-up report was written on "what measures would be required to ensure the security of theBritish Isles in the event of war with Russia in the near future".[11] American forces were relocating to thePacific region for aplanned invasion of Japan, and Churchill was concerned that the reduction of forces would give the Soviets a strong advantage for offensive action in Western Europe. The report concluded that if the United States engaged solely in thePacific Theatre, Britain's odds "would become fanciful".[12]
The Joint Planning Staff rejected Churchill's notion of retainingbridgeheads on the Continent as not having any operational advantage. It was envisaged that Britain would use its air force and navy to resist, but a threat from mass rocket attack was anticipated, with no means of resistance except forstrategic bombing.
By 1946, tensions were developing between the Allied-occupied and the Soviet-occupied areas of Europe and were considered as resulting potentially in conflict. One such area was theJulian March (an area ofSoutheastern Europe that is now divided amongCroatia,Slovenia andItaly), and on 30 August 1946, informal discussions occurred between the British and the American chiefs of staff concerning how such a conflict could develop and the best strategy for conducting a European war.[13] Again, the issue of retaining a bridgehead on the continent was discussed, withDwight D. Eisenhower preferring a withdrawal to theLow Countries, rather than toItaly, because of their proximity to the United Kingdom.