He brought the Cold War to a peaceful end
In 1989 the Berlin Wall fell, and the Cold War between East and West was brought to a halt. In 1990, the Nobel Committee gave President Gorbachev the main credit for this by awarding him the Peace Prize.
Gorbachev grew up under Stalin's regime, and experienced German occupation in World War II. After the war, he studied law in Moscow and pursued a career in the Communist Party. Journeys abroad gradually made him critical of the inefficient Soviet system, which came under further strain when the Soviet Union invaded Afghanistan in 1979.
In 1985 Gorbachev was elected the new leader of the Soviet Union. He sought to reform communism, and introduced the concepts "glasnost" (openness) and "perestroika" (change).
Society was liberalized, and Gorbachev sought détente with the USA so as to be able to transfer funding from defense to civil society. He declared that he would not support Communist regimes in other countries if their peoples were opposed to them. He thus started a chain reaction which led to the fall of communism in Europe.