Mikhail Sergeyevich Gorbachev, the former Soviet leader who played an instrumental role in ending the Cold War, has died at 91 after a “serious and long illness,” according to several Russian news agencies. He passed away at Central Clinical Hospital in Moscow.

Gorbachev took over in 1985 as the final leader of the Soviet Union before its dissolution. He brought down the Iron Curtain and sought more peaceful relations with the U.S. and the western world. Gorbachev also signed treaties that reduced the size of his country’s nuclear arsenal and withdrew troops from a nine-year war in Afghanistan.

The Soviet leader was awarded a Nobel Peace prize in 1990 for “the leading role he played in the radical changes in East-West relations,” as put by the Nobel organization.

He created a more free and democratic society in his country, initiating a policy called ‘glasnost,’ or openness, which offered more transparency as well as the freedom to criticize the government. Gorbachev also tried to implement a bold economic reform, ‘perestroika,’ meant to jumpstart the Soviet Union’s stagnant economy of the 1980s. However, his attempts to lead his country from communism to capitalism were ultimately met with widespread discontent throughout the country.

“I was doing my best in bringing together morality and responsibility to people. It’s a matter of principle for me. It was high time to put an end to the rulers’ wild cravings and to their highhandedness,” Gorbachev is quoted saying on his foundation’s website.

“There were a few things I have not succeeded in, but I don’t think I was wrong in my approach. Unless this is done, one can hardly expect that policy can play its unique part, especially now that we have entered the new century and are facing dramatic challenges.”

Gorbachev will be buried next to his wife Raisa, who died in 1999, in Moscow’s Novodevichy cemetery where many prominent Russians are also buried.