 Iran's new revolution in 1979 took the world by surprise, and the Ayatollah's threats to export ultraconservative Shi'a revolutionary influence throughout Iran's neighbouring regions eventually led Saddam Hussein's Sunni-controlled and secular Iraq, backed by the United States and the rest of the Arab world, to invade the country in 1980.The invasion signalled the start of the deadly Iran-Iraq War that would last for eight years until 1988.While Pakistan remained largely neutral, Ruhollah Khomeini's continued threats to export Iranian revolutionary sentiment fuelled tensions between Pakistan's Sunnis and Shi'as.