In 1945, as the war in Europe drew to a close, Winston Churchill was exasperated by Soviet intransigence regarding Eastern Europe, which Stalin clearly aimed to turn into a Soviet empire. Britain had gone to war in order to defend Polish independence, but at the war’s end, Stalin was riding roughshod over the Poles, keeping the third of their country he had annexed in 1939 in cooperation with the Germans, reducing them to a Soviet client state, and extinguishing their freedom and independence.
Churchill saw it as a matter touching British honor, so he ordered his generals to draw up plans for an attack on the Soviets soon as Germany surrendered, with the nebulous aim of pushing them back to the USSR’s borders, or at least forcing them to treat Poland fairly.
They presented him with Operation Unthinkable, whose title indicates what the generals thought of Churchill’s idea. Two versions were offered, an offensive and defensive one. The offensive envisaged a surprise attack on the soviets in July 1945, intended to force Stalin to give Poland a “fair deal”. The defensive envisaged a British defense of Western Europe after America withdrew from the continent. The Soviets had 10 million men available in the summer of 1945. They outnumbered the British and Americans in Europe 4:1 in men, and 2:1 in tanks – and superior tanks at that. The Allies had an advantage in the air, but even that was subject to challenge, as the Red Air Force by 1945 had formidable fighter and ground attack arms.
Moreover, the Soviet military by 1945 was not the hapless rabble it had been in 1941 when the Germans invaded, but had grown into a veteran and battle-hardened force that had won bigger campaigns against significantly greater opposition than the Allies had faced. In a nutshell, Churchill’s generals concluded that it would be ill-advised because far from being a pushover, the Red Army in 1945 was dangerous, vicious, and very big. If war broke out, it was more likely to end with the Red Army conquering all of continental Europe, rather than getting chased back to the USSR.
More importantly, it was pointed out that Britain on her own stood no chance against the Soviets, and the US had no incentive to attack them – especially not over Poland and Eastern Europe. Standing up for Poland might have been a point of honor for Churchill, but few in the British government, and fewer still in that of the US, thought Poland or Eastern Europe were worth an even greater war against the Soviet Union than the one they had just concluded against Germany.
Unlike Britain, America had never guaranteed Poland’s territorial integrity, nor had it entered WWII in order to defend Polish sovereignty. Presented with the preceding, Churchill grudgingly let the matter drop, and Operation Unthinkable was archived.