The rise of Stalinism in the USSR left the Soviet and international working class woefully ill prepared for the war. The disastrous policies of the Stalinized Communist International were critical in disarming the German working class in the face of the fascist threat, and enabled Hitler to come to power in 1933. In Spain, the Stalinists strangled the struggle of the proletariat, aiding the victory of Franco in the civil war.
Then, in the Great Terror of 1936—1938, Stalin murdered thousands of revolutionary socialists, including the entire leadership of the Red Army, which had been trained in the Russian Civil War by Leon Trotsky. In August 1939, Stalin, in the vain hope that he could thus guarantee “peace” with Nazi Germany, struck a pact with Hitler. The result was the Nazi invasion of Poland and beginning of World War II in September 1939.
Despite these crimes, the Soviet people rose up to defend the conquests of the October Revolution against the Nazi invaders. As Leon Trotsky had predicted in 1934, “should the Russian Revolution … be forced to direct its stream into the channel of war, it will unleash a terrific and overwhelming force.” In his last major work before his assassination by a Stalinist agent in 1940, In Defense of Marxism, Trotsky stressed that the Soviet Union remained a workers state, albeit a degenerated one, and had to be defended by the international proletariat against imperialism. However, the only way to truly defend the conquests of the October Revolution was through the overthrow of the bureaucracy in a political revolution by the Soviet working class, and the extension of the socialist revolution to the advanced imperialist countries.
The heroic struggle of the Red Army and the Soviet people was the decisive force in the defeat of Nazi Germany and helped inspire a wave of revolutionary struggles across Nazi-occupied Europe from 1943 onwards. It was only their betrayal at the hands of Stalinism that made possible the restabilization of capitalism after the fall of fascism and the end of the war.