The event marking the collapse of the Soviet Union in 1991 was the official dissolution of the USSR on December 26. The preceding years saw increasing political turmoil and economic instability, exacerbated by reforms initiated by Mikhail Gorbachev, such as glasnost (openness) and perestroika (restructuring). The Soviet Union faced a series of independence movements from its constituent republics, culminating in declarations of sovereignty and independence. The failed coup attempt in August 1991 against Gorbachev further weakened the central government's authority, leading to Boris Yeltsin's rise to power and ultimately resulting in the dissolution of the Soviet Union, reshaping the geopolitical landscape.