What event occurred when Iranian students invaded the U.S. embassy in Tehran?

When Iranian students invaded the U.S. embassy in Tehran on November 4, 1979, it resulted in a hostage crisis involving 50 Americans. The students took over the embassy in solidarity with the Iranian Revolution and as a protest against U.S. involvement in Iranian affairs, particularly the U.S. support for the former Shah of Iran, who had been overthrown. This act of seizing the embassy led to a 444-day standoff, during which the hostages were held captive and faced various forms of mistreatment. The incident significantly strained U.S.-Iran relations and had lasting implications for U.S. foreign policy in the Middle East.

The other options do not align with the actual events surrounding the embassy takeover. The release of American diplomats did not occur; rather, the hostages were held for more than a year. Diplomatic relations with Iran were severed, not established, following this crisis, and the assassination of American officials was not a direct consequence of this specific event.