The Soviet Union officially dissolved in 1991. Following a series of political and economic crises, along with growing nationalist movements within its constituent republics, the dissolution marked the end of the Cold War era. The push for reform by Soviet leader Mikhail Gorbachev, including policies such as glasnost (openness) and perestroika (restructuring), played a significant role in leading to the dissolution. On December 26, 1991, the USSR was formally disbanded, resulting in the emergence of 15 independent countries, significantly reshaping the political landscape of Eastern Europe and Central Asia.