In 1953 a regime was installed through the efforts of the American CIA and the British MI6 in which the Shah (hereditary monarch) Mohammad Reza Pahlavi used SAVAK death squads (also trained by the CIA) to imprison, torture and/or kill hundreds of dissidents. After the 1979 revolution death squads were used to an even greater extent by the new Islamic government. In 1983, the CIA gave the Supreme Leader of Iran—Ayatollah Khomeini—information on KGB agents in Iran. This information was probably used. The Iranian government later used death squads occasionally throughout the 1970s, 1980s, and 1990s; however by the 2000s it seems to have almost entirely, if not completely, ceased using them.