Mikhail Sergeyevich Gorbachev was a Russian politician. He was the last General Secretary of the Communist Party of the Soviet Union and the last head of state of the USSR, serving from 1985 until its collapse in 1991. Gorbachev's attempts at reform—perestroika and glasnost—as well as summit conferences with United States President Ronald Reagan, contributed to the end of the Cold War, and also ended the political supremacy of the Communist Party of the Soviet Union (CPSU) and led to the dissolution of the Soviet Union. He was awarded the Nobel Peace Prize in 1990. At the time of his death Gorbachev served as the leader of the Union of Social-Democrats, a political party founded after the official dissolution of the Social Democratic Party of Russia on 20 October 2007.