Leon Trotsky awaited the inevitable as he fed his rabbits on the afternoon of August 20, 1940. Marked for death by Joseph Stalin, the 60-year-old intellectual architect of the Russian Revolution knew that neither the armed guards patrolling the high walls of his Mexico City compound nor even the thousands of miles of land and sea that stretched between him and Moscow could completely protect him from the Soviet dictator’s deadly reach. Any thoughts of finding a sanctuary in exile had been destroyed like his bullet-riddled bedroom door when Stalinist agents stormed his villa less than three months earlier in an unsuccessful assassination attempt.

Trotsky, though, had been used to dangerous enemies since his early days as a student revolutionary in Russia. The czarist government had twice exiled him to Siberia for his Marxist beliefs. In between, the man born Lev Davidovich Bronshtein had escaped to London on a forged British passport, under the name Leon Trotsky, and met fellow revolutionary Vladimir Lenin. During the Russian Revolution of 1917, he plotted a coup of the provisional government with Lenin and formed the Red Army, which defeated the anti-Bolshevik White Army in the ensuing civil war.

Trotsky appeared to be Lenin’s natural successor, but he lost a power struggle to Stalin following the Soviet leader’s death in 1924. Trotsky became increasingly critical of Stalin’s totalitarian tactics, and his belief in a permanent global proletarian revolution ran counter to his rival’s thought that it was possible to have communism survive in the Soviet Union alone. Sensing a threat to his power, the Soviet dictator expelled Trotsky from the Politburo and the Communist Party before exiling him to present-day Kazakhstan and banishing him from the country altogether in 1929. After a four-year stay in Turkey and brief stops in France and Norway, Trotsky received asylum in Mexico in 1936.

The exiled dissident settled in Mexico City’s leafy Coyoacan neighborhood and held court with American and Mexican supporters—as well as carried on an affair with painter Frida Kahlo—while organizing the Fourth International to fight against both capitalism and Stalinism. Trotsky may have been out of Stalin’s sight, but he was never out of his mind. As the outspoken exile continued to castigate his foe, Trotsky was found guilty of treason by a show court and condemned to death.

In the early morning hours of May 24, 1940, a group of 20 gunmen stormed Trotsky’s walled compound to carry out the sentence. They sprayed the house with bullets but missed their target before they were forced to retreat. The political pariah’s bodyguards, mostly young American Trotskyites, expected the next attack would come from a bomb, so they heightened the compound’s exterior walls, bricked over windows and added watchtowers with money provided by wealthy American benefactors. “Thanks to the efforts of the North American friends, our peaceful suburban house is now being transformed, week by week, into a fortress—and at the same time into a prison,” Trotsky wrote to one of his backers.

Now, nearly three months later as the hunted man scattered food for his pet bunnies on an August afternoon, his guards continued work connecting a powerful siren on the roof when they noticed a familiar face at the compound’s gates. Frank Jacson had been a frequent caller in recent weeks. The boyfriend of a Trotsky confidante from Brooklyn named Sylvia Ageloff, Jacson was thought of as one of the family by the guards.

Along with a raincoat folded over his left arm—a strange choice of clothing on such a sunny afternoon—Jacson also carried an article that he had written and asked the revolutionary leader to review. Trotsky led the visitor to his study. Suddenly, Jacson pulled out a pickaxe with a shortened handle from inside his raincoat and buried its sharp steel tip in Trotsky’s skull. Although bleeding profusely, the expatriate managed to grapple with his attacker as guards rushed into the study. They found a dagger hidden in a secret pocket of Jacson’s blood-splattered raincoat and an automatic pistol in his hand. The bodyguards disarmed the attacker and began to beat him with the butt of his pistol until Trotsky implored them to stop, “Don’t kill him! He must talk!”

For all the preparations to prevent an attack from the outside, it ultimately came from the inside. After being rushed to the hospital along with his assailant, a conscious Trotsky at first appeared to be doing well after emergency surgery. The following day, however, he suddenly slipped into a coma and died on the evening of August 21, 1940.

Just two doors down on the hospital floor, another drama was unfolding. The battered Jacson had been carrying a confession letter, presumably to be read in case of his death, in which he claimed to be a disillusioned Belgian Trotskyite named Jacques Mornard who attacked his former hero because Trotsky had refused to bless his intended marriage to Ageloff and tried to force him to launch an assassination plot against Stalin.

Distraught at the assassination, Ageloff confirmed Jacson’s real name was Mornard, but unbeknownst to her, that wasn’t his true identity either. Their relationship had been a complete ruse, part of a Stalinist plan to kill Trotsky that had been years in the making. The assassin’s real name was Ramon Mercader, a Spanish communist recruited by the brutal Soviet intelligence agency NKVD during the Spanish Civil War. Posing as the Belgian playboy Mornard, the handsome Mercader began to seduce Ageloff after meeting her in Paris during the Fourth International meeting in 1938. The Stalinist agent followed her to the United States the following year using the passport of Frank Jacson, a Canadian who had been killed in the Spanish Civil War. When he convinced Ageloff to move to Mexico City, the spy used her ties to Trotsky to gain access to the compound and earn his trust.

Mexican authorities sentenced Mercader to 20 years in prison. Although the Soviet government denied responsibility, Stalin secretly bestowed the Order of Lenin upon the assassin. A year after his 1960 release, Mercader traveled to Moscow and received the Hero of the Soviet Union award. The assassin split time between Cuba and the Soviet Union before his death in 1978. Trotsky, who became one of the millions of Stalin’s victims, had his ashes interred under a large monolith engraved with a hammer and sickle in the garden of his Mexico City home.