The question asks to identify the Russian Marxist who was assassinated in Mexico in 1940.

Russian Marxist Assassination Details

The individual who fits this description is Leon Trotsky. He was a prominent Russian Marxist revolutionary, political theorist, and politician, often associated with Leonism and the early years of the Soviet Union alongside Vladimir Lenin.

Leon Trotsky's Life and Exile

Leon Trotsky was a key figure in the Russian Revolution of 1917. After falling out with Joseph Stalin following Lenin's death, Trotsky was exiled from the Soviet Union in 1929. He spent his years in exile in various countries, including Turkey, France, Norway, and eventually Mexico.

During his time in Mexico, Trotsky continued to be a vocal critic of Joseph Stalin's regime and founded the Fourth International, an organization aiming to promote world revolution. His political activities and writings made him a target.

The Assassination

In August 1940, Leon Trotsky was assassinated in Coyoacán, Mexico City. The perpetrator was Ramón Mercader, an agent of the Soviet secret police (NKVD), acting on orders from Stalin. Mercader used an ice axe to kill Trotsky.

Analysis of Options

• Nikita Khrushchev: While a Soviet leader, he succeeded Stalin and was not assassinated in Mexico in 1940.
• Karl Marx: A foundational theorist of communism, Karl Marx died in London in 1883 and was never assassinated.
• Joseph Stalin: Stalin was the leader of the Soviet Union during Trotsky's exile and ordered his assassination, but Stalin himself died of natural causes in 1953 and was never assassinated in Mexico.
• Leon Trotsky: Correctly identified as the Russian Marxist assassinated in Mexico in 1940.

Therefore, Leon Trotsky is the correct answer.