Trotsky had been a very important Bolshevik leader, second only to Lenin, but during the late 1920s stalin had outmaneuvered him and ousted him from the party and the country.
But not content with that the murderous sociopath stalin ordered that Trotsky be killed. A high official in the NKVD (predecessor to the KGB) planned the murder. Trotsky was living in Mexico City, protected by bodyguards. A spanish communist named Ramon Mercader worked himself into Trotsky's household and became a frequent guest. During one visit in Trotsky's office he pulled out an ice pick and buried it in Trotsky's head. Trotsky fought back, biting Mercader, and his guards arrived, alerted by his screams. But it was too late. Trotsky died in the hospital the following day.
Mercader was sentenced to only 20 years in prison. He was awarded the Order of Lenin. When he was released he went to Cuba.
I used to think badly of stalin having murdered Trotsky. But now I regard it with the same feeling I have about Vito Genovese and Carlo Gambino's murder of Albert Anastasia. They were all mass murdering sociopaths.