The other revelation from the archives is that, as the historian Vojtech Mastny has put it, there was no double bookkeeping. Marxism-Leninism was not a cover story or an ideological fig leaf for a bunch of power-mad gangsters (though gangsters they were). It was the Soviet leadership’s world view—what they really believed.

That world view is one reason that there were no immediate plans to attack Western Europe. Soviet Marxism—that is, Marxist theory as it was interpreted and dogmatized by Plekhanov, Lenin, Trotsky, and Stalin—held that capitalist states will always go to war with one another, and these wars will be a danger to socialist states like the Soviet Union. This was exactly how Stalin understood the Second World War—as a fight between capitalists.

Stalin required a security buffer on his western borders and a large military, armed with nuclear weapons, because he believed that when the capitalist countries went to war again, as the theory said they would, they would attack the Soviet Union. He also believed, as taught by the theory, that a world revolution leading to universal socialism was inevitable: it was the direction in which history was headed.