Mikhail Gorbachev was the last ruler of the Soviet Union, serving as General Secretary of the Communist Party from 1985 until the dissolution of the USSR in 1991. His policies of glasnost (openness) and perestroika (restructuring) aimed to revitalize the Soviet economy and encourage political openness. However, these reforms inadvertently led to a rise in nationalism among various Soviet republics, ultimately contributing to the USSR's collapse. Gorbachev's efforts to reduce nuclear tensions with the West and engage in arms reduction were significant, but internal challenges and economic struggles overshadowed his legacy, making the end of the Soviet Union a defining moment in world history.