Gorbachev and President Ronald Reagan at the Geneva Summit on November 21, 1985.

For most of the 20th century, the United States and the Soviet Union grappled for power, sweeping most of the world into the conflict between "communism" and "democracy."

Soviet president Mikhail Sergeyevich Gorbachev's efforts to democratize the Soviet Union's political system and decentralize its economy eventually led to the collapse of communism in Eastern Europe and the disintegration of the Soviet Union in 1991.

Upon becoming General Secretary of the Community Party in 1985, Gorbachev quickly set about resuscitating the Soviet Union's economy, which had grown stagnant during Leonid Brezhnev's term in power (1964-1982). He called for rapid technological modernization and increased worker productivity, and he tried to make the weighty Soviet bureaucracy more efficient.

From 1987-1988, Gorbachev initiated glasnost ("openness"), which called for increased freedoms of expression and information, and perestroika ("restructuring"), which instigated the first attempts to democratize the Soviet government.

Abroad, Gorbachev cultivated relations and trade with developed nations in the East and West. He consented to a withdrawal of Soviet troops from East Germany, Poland, Hungary and Czechoslavakia.

In 1990 Gorbachev received the Nobel Prize for Peace for his role in ending the Soviet Union's oppressive communist regime.

Although Gorbachev was very successful in dismantling the Soviet Union's totalitarian government, he was less willing to release the Soviet economy from the grip of centralized government. Gorbachev and his family were briefly held under house arrest between August 19-21, 1991, during a coup by Communist hard-liners. After the coup, Yeltsin's Russian government assumed leadership of the collapsing Soviet government, as various republics agreed to form a new commonwealth under Yeltsin's leadership.

On Dec. 25, 1991, Gorbachev resigned the presidency of the Soviet Union, which ceased to exist that same day.

Gorbachev's role in the collapse of the Soviet regime in Eastern Europe reinforced American ideals of democracy and freedom, and became the defining moment of the 1980s.