The United States and Iran had started to enjoy close diplomatic ties after the Second World War, until relations became strained following the 1953 coup d’état staged by the CIA and British intelligence to remove democratically elected Prime Minister Mohammad Mossadeq. America then initiated Iran’s nuclear program through the Shah of Iran, Mohammed Reza Pahlevi, who the US had backed following the coup. But the faith in the Shah was undermined and modernisation had angering Iran's religion conservatives. Religious leaders staged a revolution declaring Iran an Islamic Republic in 1979, which culminated in a US embassy hostage crisis, a severe turn in Iran-US relations. Through US chemical and biological weapons sales to Iraq in the Iran-Iraq War, the Iran backed Hezbollah bombings of 1983, the Iran-Contra Affair, the US shooting down Iranian Flight 655, followed by decades of failed diplomacy and covert operations between both nations, the current environment of extreme tension has been created.