On the afternoon of August 20, 1940, Ramón Mercader, an agent of the Stalinist secret police (GPU), attacked Leon Trotsky as he sat at his desk in Coyoacán, Mexico. Trotsky died in a Mexico City hospital the next day, August 21.

Trotsky, born in the Ukrainian village of Yanovka in Kherson province, was the co-leader with Vladimir Lenin of the October Revolution of 1917, the commander of the Red Army and the founder of the Fourth International.

Trotsky’s assassination marked the consummation of a violent counter-revolutionary assault on the cadre and leadership of the Bolshevik Revolution. Its anniversary this year coincides with the 90th anniversary of the first Moscow Trial, which opened on August 19, 1936, and began the Great Terror.

Among the accused in the first trial were the central leadership of the October Revolution and the founders of the Soviet state.

Grigory Zinoviev had been Lenin’s closest collaborator through the emigration years from 1908, chairman of the Petrograd Soviet from December 1917, and from March 1919 chairman of the Executive Committee of the Communist International. Lev Kamenev had chaired the Moscow Soviet from 1918 and, as deputy chairman of the Council of People’s Commissars, presided over the Soviet government through Lenin’s final illness.

In the two trials that followed, in January 1937 and March 1938, the accused included Yuri Pyatakov, whom Lenin’s Testament ranked with Bukharin as “the most outstanding figures” of the party’s younger generation; Bukharin himself, who had edited Pravda for a decade and whom that same Testament called “a most valuable and major theorist of the Party”; and Alexei Rykov, who had succeeded Lenin as head of the Soviet government.

The concocted basis of the trial that began in 1936 was that the accused had formed a “Trotskyite-Zinovievite Terrorist Center,” directed from exile by Trotsky, to murder Sergei Kirov in December 1934 and to assassinate Stalin and the rest of the leadership. Trotsky correctly branded the trial the greatest frame-up the world had ever seen. By 1936 the contradictions of Soviet society were mounting—the product of the bureaucracy’s program of socialism in one country, of forced collectivization and of a privileged caste consuming an ever greater share of the national income. Sixteen defendants were shot on August 25, 1936. Thirty-one more were condemned to death in the two trials that followed.

The conflict between Stalinism and Trotskyism was between two fundamentally opposed political perspectives. Thirteen years earlier, in 1923, Trotsky and the Left Opposition opened a fight against the bureaucratic degeneration of the Russian Communist Party and the Soviet state—a degeneration personified by Joseph Stalin, who had become the party’s general secretary the year before.

The programmatic foundation of the emerging Stalinist reaction was the doctrine of “socialism in one country,” first advanced in 1924. This was counterposed to Trotsky’s theory of permanent revolution, vindicated in October 1917, which held that the socialist revolution begins on national foundations but can be completed only on the world arena.

Trotsky was expelled from the party in 1927 and deported from the Soviet Union in 1929. Trotsky explained that Stalin had functioned as the “gravedigger of the revolution” and Stalinism as an agency of world imperialism. “As a conscious political force,” he wrote in The Revolution Betrayed in 1936, “the bureaucracy has betrayed the revolution” by enforcing bourgeois norms of distribution for the benefit of an upper stratum. It was, he wrote, “preparing a capitalist restoration.” The bureaucracy saw those who led the October Revolution as an impediment to be politically destroyed.

Soviet archival records count 681,692 executions in 1937 and 1938 alone. Of the 139 members and candidate members of the Central Committee elected in 1934, 98 were arrested and shot, as Soviet leader Nikita Khrushchev admitted in 1956.

Trotsky, in the 1937 essay “Stalinism and Bolshevism,” wrote that “the present purge draws between Bolshevism and Stalinism not simply a bloody line but a whole river of blood.”

As the historian Vadim Rogovin documented, the terror extended far beyond the leadership of the Bolshevik Party: scientists, educators and literary figures were murdered en masse. The poet Osip Mandelstam died in a transit camp in 1938. The writer Isaac Babel was shot in 1940, and so was the theater director Vsevolod Meyerhold. The geneticist Nikolai Vavilov was left to starve in a Saratov prison, where he died in 1943.

Nor did the killing stop at the Soviet border. Spanish police seized Andrés Nin, the leader of the POUM, in Barcelona in June 1937 and handed him to the GPU, which tortured him to death. Erwin Wolf, who had been Trotsky’s secretary in Norway, was kidnapped in Barcelona that July and never seen again. In September, the GPU gunned down Ignace Reiss, one of its own officers, on a road outside Lausanne after he broke publicly with Stalin and declared for the Fourth International. In July 1938, the GPU seized Rudolf Klement, the secretary of the Fourth International, in Paris; his dismembered body was recovered from the Seine in late August.

This was political genocide: the targeted annihilation of an entire political generation. The terror cleared the way for the pact concluded between Stalin and Hitler on August 23, 1939, which gave Nazi Germany a free hand to begin the Second World War.

At the center of the terror stood the conspiracy to murder Trotsky, who even in exile remained Stalin’s most dangerous enemy. Millions inside the Soviet Union remembered his role in the October Revolution and the Civil War and knew that the campaign against him was built on lies. Pavel Sudoplatov, the secret police officer who ran the operation, recounted in his 1994 memoir Special Tasks that Stalin gave the order in March 1939: “If Trotsky is finished the threat will be eliminated.”

The assassination conspiracy was a massive political operation, and at its center was the infiltration of the Trotskyist movement itself. The GPU’s agents were in place years before Stalin gave the order—in Paris, New York and Coyoacán—as the International Committee of the Fourth International established in its investigation Security and the Fourth International.

Mark Zborowski, the GPU’s man beside Trotsky’s son Leon Sedov in Paris, prepared the murders of Reiss and of Sedov himself, who died in February 1938 in a clinic Zborowski had chosen. Sylvia Callen, who worked as Socialist Workers Party leader James P. Cannon’s personal secretary, admitted before a federal grand jury in 1958 that she had been a GPU agent; Joseph Hansen, one of Trotsky’s secretaries in the Coyoacán household, was working for the GPU. An investigation published by the World Socialist Web Site in 2021 concluded that the evidence “leads overwhelmingly to the conclusion” that Sylvia Ageloff, who gave Mercader his entry into the household, “was an agent of the GPU who played a critical role in the assassination of Leon Trotsky.”

The murder of Trotsky was the most consequential political assassination of the 20th century—the political decapitation of the socialist movement.

Amidst all of this—the escalating campaign of terror, the betrayal of the Spanish Revolution, the approach of Stalin’s alliance with Hitler—Trotsky established the Fourth International, which held its Founding Congress in secrecy outside Paris on September 3, 1938.

Central to its founding were the program of the world socialist revolution and the crisis of revolutionary leadership. Trotsky insisted that unless the Stalinist bureaucracy was overthrown by the working class, it would restore capitalism in the USSR. The political revolution he called for was a component of the program of world socialist revolution.

The program drafted by Trotsky for the congress put it directly: “either the bureaucracy, becoming ever more the organ of the world bourgeoisie in the workers’ state, will overthrow the new forms of property and plunge the country back to capitalism; or the working class will crush the bureaucracy and open the way to socialism.”

Trotsky’s prognosis proved correct. Thirty-five years ago this week, the failed coup of August 19–21, 1991 opened the final act of the dissolution of the Soviet Union.

The men who filled the posts of the murdered made their careers on the vacancies; they became known, as Rogovin recorded, as “the newly chosen of 1937.” They ruled the Soviet Union for the next half century and brought it to the brink of collapse. The dissolution was finalized by Mikhail Gorbachev, general secretary from March 1985. On December 26, 1991, the Soviet Union formally ceased to exist.

The dissolution carved the Soviet Union into more than a dozen capitalist states. In each of them, a new ruling class was formed through the plunder of state property. In Ukraine this process has produced an oligarchy tied to Washington and Berlin; in Russia, a regime resting on Great Russian nationalism. The war between them, now in its fifth year, is the direct product of 1991. Instigated by NATO, it is conducted on the Russian side by a regime that fights not in defense of the interests of the masses but in the interests of the capitalist class that emerged from the restoration.

Ninety years after the Moscow Trials, in a new period of capitalist crisis, the agencies of world reaction are again seeking to suppress the Trotskyist movement by force. On August 10, 2026, the Pervomaisk City District Court in the Nikolaev region sentenced Bogdan Syrotiuk—a Ukrainian socialist and the leader of the Young Guard of Bolshevik-Leninists, young Trotskyists in political solidarity with the International Committee of the Fourth International—to 15 years with confiscation of property, convicting him of high treason under martial law. It also ordered the destruction of the organization’s program and printed literature.

In prosecuting Bogdan, the Ukrainian state was explicit that what it was punishing was the dissemination of the ideas of Leon Trotsky, declaring that Bogdan and the World Socialist Web Site promote “communist ideology” in the tradition of “the political current of ‘Trotskyism.’”

The court explicitly condemns Bogdan for his collaboration with the International Committee of the Fourth International. It states: “The Fourth International is a communist international organization, an alternative to Stalinism. It is based on the theoretical legacy of Leon Trotsky and sets as its task the carrying out of world revolution, the victory of the working class and the building of socialism.”

For advocacy of the perspective of Trotskyism, Bogdan has been sentenced to 15 years in prison. His persecution is a measure of the fear that the perspective of Trotskyism inspires in the ruling classes.

Throughout the world, workers and young people are entering into struggle against a social order that offers them war, inequality and dictatorship. This will produce an enormous growth of Trotskyism—the authentic Marxism of our epoch, whose heritage the International Committee of the Fourth International has defended through decades of struggle. In the perspective for which Trotsky lived and died, the program of world socialist revolution, they must and will find the way forward.