Answer: the Iran hostage crisis
The Iran hostage crisis was a diplomatic conflict between Iran and the United States. Fifty-two American diplomats were held hostage from November 4, 1979 to January 20, 1981, making it the longest hostage crisis on record.
The conflict came after Iranian students who supported the Iranian Revolution took over the U. S. embassy. In Iran, the act was seen as an act of protest against the influence of the United States in the country. In the United States, it is believed to have greatly damaged the reputation of President Carter, leading to his loss in the 1980 presidential election.