Gorbachev, who died following a long illness, was the last leader of the former Soviet Union from 1985 to 1991. "Mikhail Sergeevich Gorbachev died this evening after a severe and prolonged illness." Mikhail Gorbachev, Central Clinical Hospital, via RIA Novosti. Gorbachev was credited with introducing key political and economic reforms in the USSR. He also helped to end the Cold War. Throughout his career, the outgoing, charismatic leader strove to pass significant reforms.