The Soviet Union collapsed between 1985-1991 due to reforms introduced by Mikhail Gorbachev and rising nationalist sentiments. Gorbachev implemented policies of glasnost (openness) and perestroika (economic restructuring) in the 1980s that weakened the Soviet system. This led to independence movements in the Soviet republics. By 1991, hardliners launched a failed coup against Gorbachev and republic leaders, like Boris Yeltsin, declared independence. The Soviet Union was formally dissolved that December.