What you need to know about Iran's 1979 revolution

In February 1979, Ayatollah Ruhollah Khomeini returned to Tehran after 15 years in exile. His supporters took over police stations, courts, and government buildings, and the Iranian Army mutinied, joining the Islamic Revolution.

Thirty-one years later, hundreds of thousands of government supporters gathered in central Tehran to mark the anniversary. Meanwhile, protesters, frustrated by the government's uncompromising stance and continuing crackdown, called for the complete downfall of the 31-year-old system of clerical rule.

Images and reports on Iran's Islamic Revolution:

• Slate: A photojournalist remembers the Iranian Revolution
• Iran Chamber Society: Islamic Revolution of 1979
• BBC: Slideshow: Iranian revolution 1979
• BBC World Service: The Story of the Revolution
• Al-Jazeera: Timeline: Iran-U.S. relations
• Foreign Policy: 1979: The Great Backlash