Mikhail Gorbachev, who ended the Cold War without bloodshed but failed to prevent the collapse of the Soviet Union, died on Tuesday at the age of 91, Russian news agencies cited hospital officials as saying.
Gorbachev, the last Soviet president, forged arms reduction deals with the United States and partnerships with Western powers to remove the Iron Curtain that had divided Europe since World War Two and bring about the reunification of Germany.
When pro-democracy protests swept across the Soviet bloc nations of communist Eastern Europe in 1989, he refrained from using force - unlike previous Kremlin leaders who had sent tanks to crush uprisings in Hungary in 1956 and Czechoslovakia in 1968.
But the protests fuelled aspirations for autonomy in the 15 republics of the Soviet Union, which disintegrated over the next two years in chaotic fashion.
Gorbachev struggled in vain to prevent that collapse.
On becoming general secretary of the Soviet Communist Party in 1985, aged just 54, he had set out to revitalise the system by introducing limited political and economic freedoms, but his reforms spun out of control.
His policy of 'glasnost' - free speech - allowed previously unthinkable criticism of the party and the state, but also emboldened nationalists who began to press for independence in the Baltic republics of Latvia, Lithuania, Estonia and elsewhere.
Many Russians never forgave Gorbachev for the turbulence that his reforms unleashed, considering the subsequent plunge in their living standards too high a price to pay for democracy.
After visiting Gorbachev in hospital on June 30, liberal economist Ruslan Grinberg told the armed forces news outlet Zvezda: "He gave us all freedom - but we don't know what to do with it."