This year, the Republic of Korea began diplomatic relations with the Soviet Union in 1990, and it has been 30 years since it established diplomatic relations with communist countries such as Bulgaria and the Czech Republic. The background included Gorbachev's reform-opening (Perestroika-Glasnost) policy and the Eastern Europe Revolution of 1989, which marked a stroke in 20th century world history. The Eastern Europe Revolution, which occurred simultaneously in Hungary, Bulgaria, and the Czech Republic, triggered the fall of communism and the collapse of the Soviet Union. As a result, Eastern European countries experienced a great change as they followed the new system.