Mikhail Gorbachev, who became Soviet leader in 1985, introduced sweeping reform policies — glasnost (political openness) and perestroika (economic restructuring) — intended to revitalize a Soviet system suffering from decades of economic stagnation and political rigidity. These reforms, rather than stabilizing the system, unleashed political forces that increasingly challenged the Communist Party's monopoly on power and the union's territorial integrity, as constituent Soviet republics, particularly the Baltic states, pushed for greater autonomy and eventually outright independence.
In August 1991, a group of senior Soviet officials and military leaders, alarmed by Gorbachev's reforms and an imminent new union treaty that would have granted constituent republics considerably greater autonomy, staged a coup, placing Gorbachev under house arrest at his vacation residence in Crimea and attempting to seize control of the government. The coup collapsed within three days, undone by disorganized planning, reluctance among some military units to act forcefully against civilian protesters, and determined public resistance led by Boris Yeltsin, president of the Russian Soviet republic, who famously stood atop a tank outside the Russian parliament building to rally opposition. The coup's failure critically undermined Gorbachev's authority and dramatically accelerated the various republics' moves toward independence; by December 1991, the Soviet Union was formally dissolved, with Gorbachev resigning and Yeltsin emerging as the leader of a newly independent Russian Federation.