The dissolution of the Soviet Union (USSR) occurred on December 25, 1991, when Mikhail Gorbachev resigned as President and the Soviet flag was lowered from the Kremlin for the last time. This event marked the official end of the Cold War and the ideological struggle between communism and capitalism. The collapse was precipitated by ethnic tensions, economic stagnation, and Gorbachev's own policies of 'Glasnost' (openness) and 'Perestroika' (restructuring), which unintentionally unleashed suppressed nationalist movements. The USSR was replaced by 15 independent republics, including the Russian Federation, Ukraine, and the Baltic states. The collapse radically altered the global geopolitical landscape, leaving the United States as the world's sole superpower and triggering a difficult transition to market economies and democracy for the former Soviet territories.