In a million years I’d never have come across this on my own, but a reader points out that the documents of “Operation Unthinkable” have now been declassified—and are available online.
“Unthinkable” was Churchill’s name. As the Second World War drew to a close, he asked the British chiefs of staff a simple question: What would it take to impose upon Russia the will of the United States and Great Britain? Their answer: More than we’ve got.
In their report, which is dated May 22, 1945, the chiefs of staff write as follows (you’ll find all this on pp. 003.jpg and 004.jpg):
[T]he elimination of Russia could only be achieved as a result of:
(a) The occupation of such areas of metropolitan Russia that the war making capacity of the country would be reduced to a point at which further resistance became impossible.
(b) Such a decisive defeat of the Russian forces in the field as to render it impossible for the U.S.S.R. to continue the war.
[As for (a)]…there is virtually no limit to the distance to which it would be necessary for the Allies to penetrate into Russa in order to render further resistance impossible. It is hardly conceivable that the Allies could penetrate even as far as, or as quickly as, the Germans in 1942 and this penetration produced no decisive result.
[And as for (b)]…the existing balance of strength in Central Europe, where the Russians enjoy a superiority of approximately three to one, makes it most unlikely that the Allies could achieve a complete and decisive victory in that area in the present circumstances. Although Allied organisation is better, equipment slightly better and morale higher, the Russians have proved themselves formidable opponents of the Germans. They have competent commanders, adequate equipment and an organisation which, though possibly inferior by our standards, has stood the test.