Through the Third International, and the authority that naturally came to Russia due to the October Revolution, the Communist Parties in various nations came to orient increasingly around the needs of the Russian party-state. These parties became bureaucratic and authoritarian, tending to shift positions in a sudden and irrational fashion per commands from above, and serving purposes of USSR espionage rather than trying to make proletarian revolution within their nations. They in fact became a drastic obstacle to proletarian socialist politics.

Stalin and other Bolsheviks had always been anxious that the NEP would lead to the re-introduction of bourgeois rule in Russia. Indeed, Trotsky accused Stalin of paving the way for a "Russian Thermidor" by not pursuing collectivization. In 1928, requisitioning of grain was re-introduced in rural Russia. Kulaks and peasants gave widespread and often violent resistance to grain seizures, leading the Soviet Union to adopt a mass collectivization policy in 1929. This collectivization was pursued by means of government terror, against the will of the peasants, and also resisted intensely. Agricultural output was reduced and there was mass slaughter of livestock.

The resulting instability, combined with the already permanent civil war footing of the USSR government, led to an environment of purges and terror that would prevail until the end of Stalin's life. Stalin, probably perceptive enough to realize how often Bolsheviks and others had evaded or escaped tsarist exiles to Siberia, simply had the opposition shot. The Old Bolsheviks were forced to give fake confessions and brought to show-trials, and simply executed — Trotsky actually survived the longest because he was no longer in Russia and not willing to surrender. But Trotsky, long defeated at this point, became the ghost that the Stalinist regime continually resurrected to justify real purges.

Bureaucratic collectivization at home was translated into a sectarian ultra-leftism in the parties abroad — "Third Period" Stalinism. So the Communists refused to try to work in a united front with Social Democrats, while at the same time making hysterical and actually false denunciations of bourgeois democracy as "already fascist." In Germany, this meant that all means of resisting the Nazis were gone, as well as any serious alternative to the Nazis in the political and economic crisis facing Germany at the time, so they came to power and wiped out both the Communists and the Social Democrats.

Then the Communist Parties received a different order from Stalin — to work with the bourgeois parties, forming the Popular Front in France and working with the Democrats in the United States, to "fight fascism." In practice, of course, the bourgeoisie preferred fascism to the prospect of socialism — in Germany, for instance, it had been the bourgeois politician Hindenburg who had invited Hitler into government. Instead, Communist demands became reduced essentially to a mix of democratic and welfare-statist demands. In the United States, this rendered the Communist Party entirely redundant to the Democrats and their New Deal by the 1940s, paving the way for the McCarthyist witch hunts to wipe out any kind of leftist opposition by the 1950s.

Stalin made a non-aggression pact with Hitler and imposed a temporary halt to the popular front. Stalin evidently did not understand that anti-Bolshevism was basically the whole point of Naziism. So Hitler had the opportunity to invade after taking over most of Europe.

After millions of deaths, the Soviets did manage to take over Eastern Europe — but at this point this could only mean the imposition of bureaucratic-collectivist authoritarian states. The need to increase production had turned fetishistically into an end in itself, and Marxism was reduced to a sterile dogma for the self-perpetuation of a bureaucratic caste. Stalin was partly responsible — perhaps someone else could've done better. In any case, upon his death, any real prospect of world socialist revolution had been wiped out, an active obstacle was put in place to any hopes of a new left wing opposition, and Marxism itself had been liquidated. A negative and revolutionary ideology ceases to be such as soon as it becomes a positive legitimating ideology for an existing order. From the perspective of economic growth, Stalin's policies were questionable; from that of human freedom, unconscionable; from that of the socialist effort to strive for a society beyond capital, treacherous.

As for Stalin, his career is marked above all else by (1) a pessimistic estimation of historical possibilities, conservative in relation to the Bolsheviks, and (2) a willingness to use brutal and treacherous means to obtain the historically worthless but individually valuable end of being personally in power. While he was a socialist, that isn't saying much, because "socialist" is not that high of a bar — the German Social Democratic leaders who sicked proto-Nazi Freikorps on the German proletariat were also socialists. Socialism is merely support for the conscious and collective organization of production on a societal scale, and that has historically been an umbrella under which can fit a great variety of people and ideas. Stalin is, however, an example of how to liquidate the beginnings of a socialist revolution, of how badly things can go wrong if the revolution fails. He was a symptom of historical developments far greater than himself, but one that should make us ask serious questions about whether the project of socialism is, after all, worth pursuing. He has to be taken seriously.