When the Bolsheviks seized power in 1917, they didn’t give much thought to the foreign policy their new state would follow. Lenin admitted as much in 1921: “Before the Revolution and even after it, we thought: if not immediately then in the worst case scenario very soon, the revolution would win in other more developed countries from a capitalist point of view; if this did not occur, we would have to succumb.”

By then, the leader was forced to concede that “the movement has not been as linear as we expected.” The Bolsheviks had managed to defeat their opponents in a bloody civil war, seeing off interventions by several foreign powers, and their position looked secure for the time being. Yet European revolution had not materialized — the Soviet Union would now have to survive in a world of hostile capitalist states for a period whose length nobody could foresee.

This unexpected scenario posed a dilemma for the Bolsheviks. On the one hand, they would have to govern a vast multinational state and set about constructing a socialist economy as best they could; on the other, they had promised to direct a worldwide revolutionary movement, the Communist International (Comintern), from its Moscow headquarters. The Soviet leadership’s refusal to acknowledge the existence of any dilemma made it harder still.