Few military operations can have been given a more appropriate code name than Operation Unthinkable. As Allied armies laboriously clawed through a shattered Europe, circling and invading Nazi Germany, British military planners were considering a possible next chapter for the European theatre of conflict.
Remarkably, the plan envisaged an attack on the Soviet Union – Britain’s wartime partner and, by various measures, the strongest of the Big Three. As soon as the American, British, Canadian, French and Anzac forces had met the Russian army and had together crushed all German resistance, the plan would have seen the western allies turn on their eastern ally.
Such an attack would have been audacious, duplicitous, improbable and extremely risky. It was, in short, unthinkable. Winston Churchill held such deep suspicions for his Russian counterpart, Josef Stalin, and the communist regime that he led that he ordered the British Armed Forces’ Joint Planning Staff to think the unthinkable and plan for an attack. There was even a target date for the offensive – 1 July 1945.
Churchill’s fears were succinctly summarised in a letter he wrote to the Foreign Secretary, Anthony Eden:
“Terrible things have happened. A tide of Russian domination is sweeping forward . . . After it is over, the territories under Russian control will include the Baltic provinces, all of eastern Germany, all Czechoslovakia, a large part of Austria, the whole of Yugoslavia, Hungary, Romania and Bulgaria.
‘This constitutes one of the most melancholy events in the history of Europe and one to which there has been no parallel. It is to an early and speedy showdown and settlement with Russia that we must now turn our hopes.”
The primary goal of Operation Unthinkable was stated as being:
“to impose upon Russia the will of the United States and the British Empire. Even though ‘the will’ of these two countries may be defined as no more than a square deal for Poland, that does not necessarily limit the military commitment”.
The military’s response was unambiguous and unpromising. An attack on Russia at this stage ran a strong risk of failing – the USSR had a three to one superiority in land forces in Europe and the Middle East. The result of such failure would be the occupation of the entire European continent by the Soviet Union and the possible loss of British independence. Many hundreds of thousands if not millions of further lives would be lost.
A plan was submitted to the Prime Minister on 8 June 1945, in which the Chiefs of Staff wrote: “once hostilities began …. we should be committed to a protracted war against heavy odds”. Victory would be impossible without: “a large proportion of the vast resources of the United States”.
The plan’s obvious flaws and difficulties did not end discussions. As tensions began to increase between the west and the Soviet bloc, British and American military planners began to consider how they would defend Western Europe and the British Isles from any Russian attack.