Answer:
Gorbachev had a huge effect on European history.
He was the last head of the USSR. his policies of Perestroika (restructuring) and Glasnost (openness) were direct causes of the end of the Soviet Union. Perestroika was a restructuring of the economy which introduced some free enterprise and private property (which went against Communist belief). Glasnost was when he allowed some level of free speech, which caused all the bottled-up discontent to explode. Also, when he renounced the Brezhnev Doctrine, he allowed the satellite states to achieve full independence. The Brezhnev Doctrine had been the reason the Soviet military would invade a Soviet satellite when they were experiencing some degree of political turmoil in order to stop an overthrow of the communist regime. When this stopped, the nations were able to free themselves.
The end of Communism in the USSR meant the end of the USSR, which was the end of the Cold War. There was no more Berlin Wall, no more East Germany, no more Soviet Union. There was also more independent nations created, such as the Czech Republic, Slovakia, and the Baltic nations (Estonia, Latvia, Lithuania).