The Iranian Revolution began in 1978 as discontent with the Western-backed Shah erupted in demonstrations. Ayatollah Khomeini emerged as a leader of the opposition and helped establish an Islamic republic after the Shah fled in 1979. In 1980, Iraq invaded Iran starting the Iran-Iraq War in an attempt to gain control of a waterway, but neither side achieved major territorial gains before a ceasefire. Relations between the U.S. and Iran remain tense today due to ongoing disputes dating back to the 1979 revolution and subsequent hostage crisis.