Iran hostage crisis

The Iran hostage crisis was a diplomatic crisis between Iran and the United States. Fifty-two American diplomats and citizens were held hostage for 444 days (November 4, 1979, to January 20, 1981). 
It happened after a group of Iranian students supporting the Iranian Revolution took over the US Embassy in Tehran. President Jimmy Carter called the hostages "victims of terrorism and anarchy," adding that "the United States will not yield to blackmail."
The U.S. tried to free the hostages during the crisis, but failed when rescue officials were killed in a helicopter crash.
The hostages were released just as Ronald Reagan was being inaugurated as President.