The USA and Iran have been at loggerheads since 1979 when a revolution in Iran brought to an end an American leaning regime.
Sixty-six American hostages were held at the American Embassy in Tehran for 444 days. They were released after Ronald Reagan became the president in 1981; fueling rumours that hostage crisis played a role in defeat of Democrats led by Jimmy Carter. Iran thereafter became an Islamic Republic led by religious leaders, a theocracy.