As so often the theory was one thing and the practice another. The belief that Communism was better than Nazism stops us seeing that the Bolshevik Revolution was an insane idea from its inception. A "vanguard" party, composed of a tiny band of professional revolutionaries, could hold on to power only by terrorising the subject population. The Bolsheviks had to crush independent Jewish organisations, as they had to crush all other independent organisations. Yet even before the Bolsheviks produced a left-wing variant of the Nazi conspiracy theory, the Jews were a special case in the old Soviet Union. The Bolsheviks recognised other minorities as minorities with homelands. They never said that there should be a Jewish homeland in their empire. Socialist Zionism was a particular threat to the new regime. If Jews succeeded in building a socialist state in Israel, it would be a rival. Lenin set a loyalty test. Before he came to power, he purged the Communist movement of supporters of the Bund. The only Jews he permitted to remain were Jews who were so thoroughly assimilated that they were barely Jews at all.

Unlike Lenin, Stalin was an anti-Semite and understood the uses of irrational hatred. His crimes took the forms of the sins of omission and commission. The omission was not to see Nazism for what it was, and ally with it in the Hitler-Stalin pact of August 1939. It remains one of the most hypocritical and stupid acts in the annals of diplomacy, where examples of hypocrisy and stupidity are not hard to find. Throughout the 1930s Communist writers, poets and propagandists had denounced fascism and urged a popular front against the Hitlerian menace. Then in August 1939 Stalin stood on his head and announced a Soviet reconciliation with Nazi Germany so they might partition Poland between them. Stalin believed in Hitler. Solzhenitsyn speculated in The First Circle that Hitler was the only man he ever really trusted. The complete surprise Hitler achieved when he invaded an unprepared Soviet Union in 1941 suggests that Solzhenitsyn was right. By signing the pact, the Soviet Union agreed to hand over the Jews of western Poland to the Nazis. Although conventional historians lazily say that the pact shocked a generation of leftists, Shindler points out that membership of the British Communist Party actually rose after the tyrants had cut a deal, and hardly anyone worried about the fate of Polish Jewry. Those who had shouted loudest about the dangers of fascism from 1933 to 1938 were as willing as Chamberlain and Halifax to appease it in 1939.

Leftists of the 1968 generation tried to recover something from the disgrace of Marxism-Leninism by arguing that if only Trotsky had succeeded Lenin then all would have been well. Trotsky, however, argued from exile that the war between Nazi Germany and Britain and France was an imperialist conflict. Marxists should not take sides, but wait for the revolutionary opportunities that would follow the exhaustion of the warring powers. Shindler illustrates the mood far beyond the Communist Party by digging up the writings of Tony Cliff, the cultish founder of the Socialist Workers Party, the most malign force in British left-wing politics. "Tony Cliff" was the suitably proletarian nom de guerre of Ygael Gluckstein, who was born in Palestine. In our day, the SWP accuses virtually everyone of being a fascist, most notably Israelis and their friends abroad. Yet when he confronted actual fascists in the form of Nazi armies, Gluckstein would not fight them. If Rommel had broken through the British lines at El Alamein, the Nazis would have killed every Jew in Palestine, including Gluckstein. Instead of defending them and himself, he issued appeals to Jewish students not to fight Hitler that were so insistent the British authorities interned him alongside members of the Stern gang in Acre prison. The Trotskyist thought he could secure a revolution and throw out the British imperialists by letting the Nazis win. Stern and his associates thought they could create a Jewish state by attacking the British and trying to negotiate with the Nazis. It is hard to say who was the greater fool.

The establishment of Israel in 1948 and its defeat of the first Arab attacks unleashed the sins of commission. The idea that Soviet Jews wanted to flee their glorious socialist motherland to Israel persuaded Stalin to ape the tactics of Hitler. The secret police began rounding up Jewish writers on charges of Zionism just four years after the overthrow of the Nazis. Stalin turned on Jewish Communist leaders across the new Soviet empire. In 1953, in his last days, he imagined a plot by Jewish doctors to poison him and the Soviet leadership. Historians dispute what would have happened if Stalin had lived, but it is possible that he would have deported the remaining Jews of European Russia to central Asia. Even after his death, the Polish Communist Party distracted attention from student protests by launching Europe's last pogrom in 1968.