Final answer:
The Iranian Hostage Crisis was the longest US hostage situation, with 52 Americans held at the US embassy in Tehran for 444 days until their release on January 20, 1981.
Step-by-step explanation:
Initiated by the storming of the US embassy by Iranian students on November 4, 1979, the Iranian Hostage Crisis was a pivotal moment in US-Iran relations. This event followed the admission of the Shah into the United States for medical treatment, sparking fears of a reinstated monarchy backed by the US. Demands were made for the Shah's return to Iran for trial, a sentiment endorsed by the newly-revolutionized Iranian state under Ayatollah Khomeini.
While some hostages were released early on, the majority remained captives until the end of President Carter's term on January 20, 1981, coinciding with Ronald Reagan's inauguration. The duration of their captivity was used politically by Iran to assert leverage and by Reagan to project an image of renewed American strength. The crisis ended with a negotiated release of the hostages, coinciding with the unfreezing of nearly $8 billion in Iranian assets. The legacy of the crisis impacted US foreign policy and presidential politics for years to follow.