Marx's error, Hitler believed, had been to foster class war instead of national unity - to set workers against industrialists instead of conscripting… - Daniel Hannan

The two armies [Red Army and Nazi Army] met at the town of Brest, where the 1918 peace treaty between the Kaiser’s government and Lenin’s revolutionary state had been signed. Soldiers fraternised, exchanging food and tobacco – pre-rolled German cigarettes contrasting favourably against rough Russian papirosi. A joint military parade was staged, the Wehrmacht’s field grey uniforms alongside the olive green of the shoddier Soviets. The two generals, Guderian and Krivoshein, had a slap-up lunch and, as they bade each other farewell, the Soviet commander invited German reporters to visit him in Moscow “after the victory over capitalist Albion”.

The two totalitarian systems [USSR Communism and German National-Socialism] traded in all the necessary commodities of war: not just oil and vital chemicals, but arms and ships. They exhibited each other’s cultural achievements, performed each other’s music and films, stressed their joint hostility to Western capitalism.

The idea that there was an unbridgeable gap between Soviet Communism and National Socialism, which is nowadays so widespread, would have seemed curious at the time. To be sure, there were some in Moscow, and a few more in Berlin, who believed that there must eventually come a reckoning with their “real” enemy. But theirs were minority voices. Many more gladly went along with the idea that the two socialist systems were joined in battle against “decadent Anglo-Saxon liberalism”.