Mikhail Gorbachev did not set out to destroy the Soviet Union. He wanted to save it. His reforms of glasnost and perestroika were designed to modernize a stagnating superpower, not dismantle it. But the forces he unleashed — transparency, political openness, economic restructuring — proved impossible to control, and on Christmas Day 1991, the Soviet flag came down for the last time.

This episode traces Gorbachev from his rise through the Communist Party ranks to the reforms that cracked the empire open, the failed coup that sealed its fate, and his strange afterlife as the most admired Russian leader abroad and the most reviled at home.

• How Gorbachev rose through the Soviet system as a reformer in a gerontocracy
• Glasnost and perestroika — the reforms that spiraled beyond anyone's control
• The 1991 coup attempt and  ...