As a result of a revolution in Iran during 1978 and 1979,

As a result of the Iranian Revolution, the pro-American government of the Iranian Shah Reza Pahlavi, was replaced by the more extreme religious theocracy led by Ayatollah Khomeni. The transition included the takeover of the U. S. Embassy in Teheran and the seizure of more than 40 U. S. hostages. The United States subsequently cut off diplomatic relations with the Iranians for a number of years.