20 August 1940 year

In Mexico City, an NKVD agent Ramon Mercader attacked the former People's Commissar of Military Affairs with an ice pick Leon Trotsky. A day later he died in the hospital.
Destroy the vermin! Wipe the enemy of the people Trotsky and his bloody fascist gang from the face of the earth!
(Soviet poster from 1937)
"Did Stalin poison Lenin?"
(the title of Trotsky's article in Liberty magazine, published 10 days before the assassination)
In the morning, 60-year-old Trotsky, expelled from the USSR by Stalin and already living in exile for 11 years, was in excellent spirits. He slept at his villa, rubbed himself down, fed the rabbits, and planned to work "properly." That day, he was preparing articles on military mobilization in the United States and the "exposure" of Stalin.
After lunch, a lawyer came to see him in the case of a recent assassination attempt - on May 24, 1940, a group of Soviet agents led by a Mexican artist and Stalinist David Siqueiros Trotsky's house was stormed, but he managed to hide with his wife and grandson. By that time, he was already "confidently expecting an assassination attempt"—back in March, the Mexican Communist Party Congress had officially declared a course to exterminate "Trotskyism." Who was behind the attack also understood.
Tradition, schooling, vast resources, and a wide selection of performers are evident. This is the work of the GPU.
As I was informed, Stalin admitted several times that my exile abroad was a “greatest mistake” [Trotsky was successful in exile, founding the opposition Fourth International and publishing the Bulletin of the Opposition]. To correct the mistake, there was nothing left but an act of terrorism.
For the second time, the killers of the “best” (according to Lenin) Bolshevik chose a different strategy: on August 20, at a little after five, a Canadian businessman and convinced Trotskyist came to see Trotsky. Frank Jackson, to show his manuscript. In fact, it was the Spanish communist and recruited NKVD agent Ramon Mercader.
I asked him: "Why are you wearing a hat and a cloak?" (The cloak hung on his left arm, pressed to his body). He always boasted that he wore neither a hat nor a cloak in the worst weather. He showed me several sheets of paper [of manuscript] typewritten. He took them out with a constrained movement of his hand, continuing not to lift it from the body and pressing the cloak, in which, as it later became known, an axe and a dagger were sewn.
(Trotsky's wife, Natalia Sedova-Trotskaya)
Three or four minutes after Trotsky began reading the manuscript in his office, Mercader hit him on the head with an ice axe.
I heard a terrible, shocking scream. Lev Davidovich stood leaning against the doorframe, his face bloodied. He said to me calmly, without indignation or bitterness or annoyance: "Jackson." He said it as if he wanted to say, "It's done."
(Natalia Sedova-Trotskaya)
Trotsky managed to raise a fuss and call for security. But the wound in his skull was too deep (about seven centimeters), and he died in the hospital a day later.
A man whose name is spoken with contempt and curse by workers around the world has gone to his grave. Foreign intelligence agencies have lost a long-serving, seasoned agent who shunned no means to achieve his counterrevolutionary goals.
(Pravda newspaper, August 24, 1940)
The Soviet government denied any involvement in Trotsky's murder. He was cremated and buried in a villa in Mexico City five days after his death—during which time tens of thousands of people passed by his body, which was laid out for farewell.
Trotsky ordered his guards to leave his killer alive. During the investigation, he identified himself as Belgian. Jacques Mornard, He explained his actions as an act of retaliation by a lone fighter and refused to testify. It was not possible to uncover his agent connections to the Union at the time.
A Mexican court sentenced him to the maximum penalty—20 years in prison. In 1960, after his release and return to the USSR, Mercader was awarded the title Hero of the Soviet Union, the Order of Lenin, and given a state dacha and a four-room apartment. Only a few close associates knew about his past.
Trotsky was rehabilitated only in 1992—not for the murder, but for his expulsion to Siberia and from the USSR. To this day, there is no public evidence of his work for foreign governments.