Meanwhile, the Allies had to reckon on the war expanding as the Soviets attacked Norway, Greece and Turkey (ominously, British planners expected the Soviets to ally with Japan). As for the atom bomb, the United States only had two in the summer of 1945, and they were earmarked for Japan. By 1946, America had only nine bombs. Powerful as they were, they could only inflict a fraction of the punishment that the Soviet Union suffered at the hands of the Nazis—and still kept on fighting.

What’s fascinating isn't just the hubris—or chutzpah—of Britain invading Russia, something which it hadn't done since the Crimean War. It's the assumptions behind the plan, driven either by wishful thinking or sheer desperation.

Even as the death camps were being liberated, Britain contemplated rebuilding a German army to fight the Russians. “One of the most contentious issues in the Unthinkable plan was the use of German forces within the Allied camp,” Walker writes. “It was anticipated that ten German divisions could be utilized for offensive operations, but because it would take time for them to be re-equipped from Allied sources, the units would not be ready for 1 July and would only become available in the autumn; that they should be used at all was likely to be highly controversial.”

But rearming ex-Nazis paled in comparison to an absolute foundation of Operation Unthinkable, which was that the United States would join Britain in attack on the Soviet Union. Roosevelt, and initially Truman until he knew better, were convinced that it was possible to work out a postwar accommodation with Stalin. They were wrong, but they didn't know that in the spring of 1945. And there was still the victory with Japan to be won—for which Soviet help was considered essential. In other words, America had just finished a crusade in Europe against Nazism. It wasn't about to embark on a crusade against Communism just yet.

Military buffs love to debate how a war between the Western Allies and Soviets would have turned out (though the assumption is usually that the Soviets would have attacked first). Enthusiasts love to argue the merits of Sherman vs. T-34 tanks, or P-51s versus Yak fighters. It's all very interesting, and almost totally pointless.

The rock-bottom fact of a war that would have dragged the world into World War III is this: Operation Unthinkable called for the democratic nations of the United Kingdom and the United States to initiate a war with the Soviet Union. The justification would have been the need to roll back the Soviet empire from its German and Eastern European conquests.

In return, the populations of Britain and America would be expected to endure a protracted conflict with no certain means of compelling the enemy to surrender. Rather than the relatively bloodless air and naval warfare that the Anglo-Americans preferred and still prefer, they would have been trapped in a land war with the world's foremost land power, on the vast, cold plains and swamps of Eastern Europe.

Operation Unthinkable was truly unthinkable.

Further reading: Operation Unthinkable: The Third World War: British Plans to Attack the Soviet Empire 1945.

Michael Peck is a contributing writer for the National Interest. He can be found on Twitter and Facebook.

Image: Wikimedia Commons / Archangel12.

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