By Stephen Kotkin

Penguin Press. 1,154 pp. $40

A frenzy of hunting for spies and subversives shook the Soviet Union in the late 1930s, as Joseph Stalin propelled his police to unmask Trotskyite-fascists, rightist and leftist deviationists, wreckers and hidden enemies with party cards. Yet if we apply the perverse logic of Stalinism, the greatest subversive agent to undermine the promise of the revolution of 1917 and transform the aspirations of millions into bloody despotism — objectively, as Stalinists would have said — was the dictator himself. Stalin killed more communists and did more to undermine the international communist movement than Adolf Hitler did. Rather than Lenin’s comrades Lev Kamenev, Grigory Zinoviev, Nikolai Bukharin and Lev Trotsky allying with Hitler, as they were falsely accused of doing in the great show trials of 1936-1938, it was Stalin who in 1939, as Trotsky explained, advanced “his candidacy for the role … of Hitler’s main agent.”

In “Stalin: Waiting for Hitler, 1929-1941,” a mammoth volume of more than 1,100 pages, Princeton University historian Stephen Kotkin presents in vivid, irresistible and unrelenting detail that part of Stalin’s life — and Soviet history — that has, more than any other, fascinated scholars and general readers about the Soviet experience. The 1930s was the decade of the “revolution from above” that dispossessed peasants and converted them into agricultural suppliers to the state, the city and the army; it was the time when the state unleashed mass terror against elites and ordinary people that decimated the Soviet Communist Party; decapitated the Red Army; disciplined the intelligentsia into straitjacketed conformity; and drove millions of people into exile, prison camps and emigration, if they managed to survive. In one year, 1937-1938, between 700,000 and 800,000 Soviet citizens and unfortunate foreigners in the country were executed. Stalin proclaimed that collectivization, the end of market relations and the descent into despotism were in fact the building of socialism – and the author of this volume agrees — but to Stalin’s critics on the left (Trotskyists, Social Democrats and independent Marxist intellectuals) they were the “revolution betrayed,” a sanguinary counterrevolution.

The very heft of the book, which is the second volume of a planned trilogy, testifies to Kotkin’s prodigious research and diligent assembling of material. A veteran of Stalin studies, Kotkin focuses on the despot and relates who entered and left his office, what documents (many of them denunciations and thousands of torture-induced confessions) landed on his desk, and who was in favor and who had fallen out. The police supplied Stalin with stories of spies and saboteurs. The steady stream of intelligence reports possessed Stalin, feeding the dictator’s predilection for uncovering conspiracies and plots, many of them deliberately fabricated. Kotkin’s story moves from Stalin’s office, known as the Little Corner, beyond the Kremlin, ranging widely through the swirling events in Europe and Asia that Stalin believed presented existential dangers to his regime and his socialist project.

The Soviet Union was profoundly isolated, as was Stalin himself, particularly after the suicide of his wife in 1932 and the murder of his friend Sergei Kirov in 1934. Hitler was visible on the horizon; Spain was riven by a civil war that many saw as the first round of the future battle between fascism and communism; and enemies plotted against the U.S.S.R. on the Soviets’ far-flung borders, from Poland in the west to Japan in the east. A constant source of anxiety was Britain, the country that Stalin consistently imagined as the greatest danger. Stalin’s “worldview and governing style,” his imagining of enemies within the country, his sensitivity to any personal slight or perceived, potential opposition, and his ruthlessness at destroying those whom he believed might pose a future threat gravely weakened his state and society on the eve of invasion and war.

A central mystery lurks at the heart of this book: Why did Stalin launch the Great Terror, which damaged so profoundly the very system he painstakingly built? Kotkin moves beyond some of the more familiar explanations – Stalin’s unwillingness to settle for a spot at the top of the bureaucracy, a search for unity within the country inspired by the negative example of divisions on the left in Spain, or Stalin’s personal paranoia. Rather, he contends that the cause lies in a particular mentality that originated in Marxism and lethally meshed with Stalin’s peculiar psychology. “The combination of Communist ways of thinking and political practice,” he argues, “with Stalin’s demonic mind and political skill allowed for astonishing bloodletting.”

“Perceived security imperatives and a need for absolute unity once again turned the quest in Russia to build a strong state into personal rule. … Tyranny has a circular logic: once a dictator has achieved supreme power, he becomes keener still to hold it, driving him to weed his own ranks of even potential challengers.” As damaging as the purges were, Stalin was not irrational, Kotkin contends, but calculating and strategic. The dictator believed that the replacement of a contentious, competitive elite of old communists with younger, Soviet-trained, presumably more loyal cadres, as well as mobilizing people through fear, were effective ways to preserve the Soviet system and his power. Stalin emerges as a murderous pedagogue, using violence to teach his people how to behave. He told subordinates to check their underlings by punching them in the face. Ultimately he would do far worse, making fateful, fatal decisions based on the documents he read and on his own intuition.

Interspersed with domestic disasters, the narrative veers into the thickets of foreign policy, and Kotkin presents the story of the unthinkable alliance of Hitler and Stalin in the August 1939 Molotov-Ribbentrop Pact as Stalin’s triumph. While the British and French frittered away the possibility of an agreement with the Soviets, Hitler seized the bait offered by Stalin to launch his war of destruction against Poland without fear of a two-front confrontation. Not only did Stalin gain time to prepare for the eventual war with Germany that he anticipated but wished to avoid, he also was handed carte blanche in the Baltic republics, Finland and Bessarabia. His destructive policies within the Soviet Union that can hardly be described as fully rational are contrasted with his ruthless, unsentimental realpolitik in foreign policy.

Kotkin builds on the mountain of previous scholarship on Stalin and Stalinism but has his own, sometimes idiosyncratic (but always intriguing) take on major issues. “Hitler,” he states categorically (as he is wont to do), “was at least as great a threat as Stalin.” Really? Well, maybe not, because in the next paragraph he qualifies this assertion: “Despite Stalin’s domestic house of horrors, as well as the Comintern’s unscrupulous, albeit often pitiful, machinations abroad, the main armed, expansionist power seeking domination in Europe was Nazi Germany. … Hitler’s Versailles revisionism was unlimited; Stalin’s was limited to opportunities others might present.”

An engaging writer, Kotkin for some reason decided in this volume to adopt a rigidly chronological organization of his history with an almost day-by-day recounting of events. Such an approach gives readers a sense of the kaleidoscope in which Stalin was forced to work, but at the same time it leads to a kind of mental whiplash. The strict chronicling of events might jerk from one paragraph on the conflicts in China between communists and nationalists, to another taking us into the tyrant’s family circle, to the next inside the mind of Hitler. The book has a hurried quality about it, so one appreciates those sections when, after masses of information and shocking stories of callous brutality, the author occasionally pauses and does the hard work of synthesis, interpretation and explanation.

But no biography or history is definitive, no matter what publishers’ publicists proclaim, and anyone with the time and upper-arm strength to prop up the book will experience an exhausting, exhilarating journey. Kotkin masterfully guides us through the turbulent years of Stalin’s long wait for Hitler’s invasion, a profoundly tragic time for the Soviet people and the fate of democracy and socialism.

Ronald Grigor Suny is the William H. Sewell Jr. professor of history at the University of Michigan and the author of “Red Flag Unfurled: History, Historians, and the Russian Revolution.” His next book is a biography of Stalin before the revolution.