Rocky IV is a 1985 American film written by, directed by, and starring Sylvester Stallone. It is the fourth and most financially successful entry in the Rocky franchise. In the film, Rocky Balboa plans to retire from boxing after regaining his title from Clubber Lang. A Soviet boxer named Ivan Drago, nicknamed ‘The Siberian Express’, comes to the United States with his wife, a Russian champion swimmer and coach for a guest match.
Drago is a superbly conditioned boxer who has been scientifically trained in the USSR. Apollo Creed decides to take on Drago despite having been out of the ring for several years. Creed unwisely taunts Drago before the match, and after the first round, Drago issues a prophetic warning to Creed: “You will lose.”
Unfortunately the warning comes true and Creed dies following a pounding by the Siberian Express. When death threats are made against the Russian boxer, he returns to the USSR and states if there is to be a match between Balboa and Drago, it will be in the USSR.
To honor Creed’s memory, Rocky takes the Soviets up on their challenge and goes to Siberia to train for the match that will take place in Moscow on Christmas Day, in front of a hostile audience. It proves to be the toughest match of his life.
Summary via Wikipedia.