Describe the collapse of the Soviet Union. Begin with the events during the 1980s including the entire Gorbachev era. Should include at least the following topics:
1. Poland's democratic revolution of the 1980s
2. Gorbachev
3. perestroika
4. Chernobyl nuclear disaster
5. glasnost
6. Warsaw pact breakup in 1989
7. Lithuanian independence movement
8. Boris Yeltsin
9. August coup of 1991