The Soviet Union dissolved in 1991, officially marking the end of the Cold War era. This dissolution followed years of political and economic turmoil, catalyzed by reforms initiated by Mikhail Gorbachev, including glasnost (openness) and perestroika (restructuring). The weakening grip of central authority led to rising nationalist movements in various Soviet republics, culminating in declarations of independence from countries like Ukraine, Estonia, and Lithuania. The final blow came on December 25, 1991, when Gorbachev resigned, and the Soviet Union was officially disbanded into 15 independent republics, fundamentally reshaping the geopolitical landscape and ending communist control in Eastern Europe.