For both men, mass murder was just another weapon in the ideological struggle. The state, whether Communist or Nazi, was supreme; individuals were its disposable tools. They even extended this idea to their domestic lives. Hitler had secret mistresses, most notably Eva Braun, but in public no woman was allowed to come between him and his nation. One of his secretaries recalled that he used to emphasize again and again: "My lover is Germany." Stalin married twice and had children, but the suicide of his second wife, Nadya, in 1932 further brutalized him. Echoing Hitler, he once remarked: "A true Bolshevik shouldn’t and couldn’t have a family because he should give himself wholly to the party." Stalin told his son, Vasily: "I’m not Stalin … Stalin is Soviet power."

The Nazi–Soviet pact inextricably linked these two extreme proponents of totalitarian violence. Eight days after its signing Hitler invaded Poland and Stalin publicly supported his Nazi collaborator, announcing to the world in the Communist Party newspaper Pravda: "It is not Germany who has attacked England and France, but England and France who have attacked Germany." The enslavement of Poland united them in blood. SS units killed 60,000 Jews and members of the Polish ruling class. It was Hitler’s first experience of mass murder and profoundly influenced him, showing him his followers would actually do it. Stalin’s secret police, the NKVD, long versed in mass killing, would carry out similar massacres in the east of Poland. Among their victims were more than 20,000 Polish officers and political prisoners whose bodies would be discovered three years later.

Stalin had entered his pact with Hitler with open eyes and never doubted he was supping with the devil. However, he believed the pact offered the Soviet Union both protection and opportunity, telling his inner circle just a week after the Nazis invaded Poland: "A war is on between two groups of capitalist countries. … Hitler, without understanding it or desiring it, is shaking and undermining the capitalist system. … We can manoeuvre, pit one side against the other to set them fighting with each other as fiercely as possible." He was also eyeing up a further desirable outcome, the chance to expand his communist empire: "What would be the harm if, as a result of the rout of Poland, we were to extend the socialist system onto new territories and populations?"

For Hitler the pact also opened the door to conquest. Having cleared the potential threat to his rear, he could now turn all his energy and attention to planning the invasion of France. On October 1, 1939, Goebbels noted that he was even starting to hint at a desire for long-term collaboration with Stalin: "Conference with the Führer in private. He is convinced of Russia’s loyalty. After all Stalin is set to pocket a huge profit." However, Stalin saw no such potential loyalty in Hitler. Mein Kampf was still etched in his mind, above all Hitler’s youthful ambitions to conquer Russian territory for the new German Reich: "If we speak of territory in Europe today, we can primarily have in mind only Russia and her vassal border states."

Because he calculated that Hitler might still one day turn on him, Stalin set out to build a line of buffer zones to protect himself against possible Nazi attack. He forced the Baltic states, Lithuania, Estonia and Latvia, to accept Russian garrisons and on October 3, 1939, told a Latvian delegation: "There has been an unexpected turn, but one cannot rely upon it. We must be prepared in time. Others, who were not prepared, paid for it. The Germans might attack."

Stalin also tried to bully Finland into giving him a swath of territory to provide a salient around Leningrad as a further buffer. When the Finns refused, Stalin sent in the Red Army. It was a disaster. Within days thousands of frozen Russian corpses littered the snow and, although the Finns were finally beaten by sheer weight of numbers and machinery, they managed to kill 125,000 Russian soldiers in the bloody "winter war."

Reprinted from Warlords, Copyright 2006. Reprinted by permission of Da Capo Press.