When Gorbachev came to power in 1985 at age 54, the idea that the Cold War could end, the Iron Curtain could melt fairly peacefully, that fear of a nuclear conflict between two superpowers could subside, and that millions of people could gain more democratic freedoms, was seemingly an impossible dream.
Gorbachev sparked a revolution over a momentous six-year period from 1985 to 1992 by daring to reach out to the West and push through needed reforms at home, ultimately at his own political cost.
At that time, the Soviet political system was heavily bureaucratic and rife with corruption; the economy was weak with regular shortages of goods; and political dissidents filled gulags.
Gorbachev's major changes were too sudden and deep for Russia's economy to cope with and millions of people there suffered hardship. The loss of political status - which continued later as some former Soviet bloc countries defected to Nato and the European Union - was a blow to its nationalistic pride. By August of 1991, there was an attempted coup and Gorbachev resigned as Soviet leader that Christmas.
Hence, Gorbachev's divisive reputation in Russia that helped eventually bring President Vladimir Putin to power. He has been rolling back the Soviet leader's legacy in the country, dealing with the West on different terms, and trying to restore a dead empire state of mind in Ukraine.
A Communist who wanted to develop the Soviet project rather than end it, Gorbachev was motivated to try to improve it, and take off mental and monetary shackles.
Gorbachev's political and economic reforms - meant to bring about more gradual, controlled change - were the accidental hole that cracked the dam. The gush of people power that followed was impossible to contain.
Although his goals were limited in scope, the scale of the challenge to make Russia more modern, open and engaged with the outside world was still massive. Simply believing it could be done required boldness and bravery and a belief he could make a difference.
Gorbachev was a man Western leaders could work with. The first indication of a thaw in wintry relations came when Gorbachev met US President Ronald Reagan at a summit in Geneva in November 1985.
He oversaw two treaties with the US to cut nuclear weapons; the withdrawal of thousands of troops from Soviet bloc countries and Afghanistan; and encouraged East German leaders to open the Berlin Wall, allowing free passage which played a key role in German reunification. The Chernobyl accident in Ukraine in 1986 showed what was at stake with nuclear power and weapons under the Soviet system's control.
Putin is the antithesis of Gorbachev, focused on projecting strength through fear and intimidation, a modern paranoid tsar obsessed with the past rather than the future. He called the collapse of the Soviet Union the "greatest geopolitical catastrophe of the 20th Century".
As an authoritarian opposed to liberalism, Putin's rule features the old pre-Gorbachev tactics of political control, suppressing the independent media, and attacking dissidents.
Putin is trying to bring Ukraine to heel by force. During the 1989 uprisings in eastern European satellite states, Gorbachev did not crack down on them. But force was used during unrest in other states such as Lithuania, Azerbaijan and Georgia.
The hope for a better future for Russia lies with younger people who may be inspired by Gorbachev's example. Some potential future leaders may be exiles lost to other countries or tragic drone fodder on Putin's battlefields. Putin's chief opponent, Alexei Navalny, is being kept quiet in prison.
Outside Russia, the Gorbachev of his heyday continues to make most other leaders look small and ineffective, even with climate change being the equivalent issue of the day.
