On November 4, 1979, 52 United States diplomats and citizens were held hostage after a group of militarized Iranian college students belonging to the Muslim Student Followers of the Imam's Line, who supported the Iranian Revolution, took over the U.S. Embassy in Tehran and seized hostages. A diplomatic standoff ensued. The hostages were held for 444 days, being released on January 20, 1981.

Western media described the crisis as an "entanglement" of "vengeance and mutual incomprehension". U.S. President Jimmy Carter called the hostage-taking an act of "blackmail" and the hostages "victims of terrorism and anarchy". In Iran, it was widely seen as an act against the U.S. and its influence in Iran, including its perceived attempts to undermine the Iranian Revolution and its longstanding support of the shah of Iran, Mohammad Reza Pahlavi, who was overthrown in 1979. After Shah Pahlavi was overthrown, he was admitted to the U.S. for cancer treatment. Iran demanded his return in order to stand trial for crimes that he was accused of committing during his reign. Specifically, he was accused of committing crimes against Iranian citizens with the help of his secret police. Iran's demands were rejected by the United States, and Iran saw the decision to grant him asylum as American complicity in those atrocities. The Americans saw the hostage-taking as an egregious violation of the principles of international law, such as the Vienna Convention, which granted diplomats immunity from arrest and made diplomatic compounds inviolable. The Shah left the United States in December 1979 and was ultimately granted asylum in Egypt, where he died from complications of cancer at age 60 on July 27, 1980.

Six American diplomats who had evaded capture were rescued by a joint CIACanadian effort on January 27, 1980. The crisis reached a climax in early 1980 after diplomatic negotiations failed to win the release of the hostages. Carter ordered the U.S. military to attempt a rescue mission Operation Eagle Claw using warships that included USS Nimitz and USS Coral Sea, which were patrolling the waters near Iran. The failed attempt on April 24, 1980, resulted in the death of one Iranian civilian and the accidental deaths of eight American servicemen after one of the helicopters crashed into a transport aircraft. U.S. Secretary of State Cyrus Vance resigned his position following the failure. In September 1980, Iraq invaded Iran, beginning the IranIraq War. These events led the Iranian government to enter negotiations with the U.S., with Algeria acting as a mediator. The crisis is considered a pivotal episode in the history of IranUnited States relations.Political analysts cited the standoff as a major factor in the continuing downfall of Carter's presidency and his landslide loss in the 1980 presidential election; the hostages were formally released into United States custody the day after the signing of the Algiers Accords, just minutes after American President Ronald Reagan was sworn into office. In Iran, the crisis strengthened the prestige of Ayatollah Ruhollah Khomeini and the political power of theocrats who opposed any normalization of relations with the West. The crisis also led to American economic sanctions against Iran, which further weakened ties between the two countries.

Ronald Wilson Reagan ( RAY-gən; February 6, 1911 – June 5, 2004) was an American politician who served as the 40th president of the United States from 1981 to 1989. A member of the Republican Party, he previously served as the 33rd governor of California from 1967 to 1975 after a career as a Hollywood actor and union leader.

Reagan was born to a low-income family in Tampico, Illinois. He graduated from Eureka College in 1932 and began to work as a radio sports commentator in Iowa. In 1937, Reagan moved to California, where he found work as an actor and appeared in several major productions. From 1947 to 1952, Reagan served as president of the Screen Actors Guild, during which time he worked to root out alleged communist influence within it. In the 1950s, he moved to a career in television and became a spokesman for General Electric. From 1959 to 1960, he again served as president of the Screen Actors Guild. In 1964, his speech "A Time for Choosing"—a campaign speech on behalf of Republican presidential nominee Barry Goldwater—earned him national attention as a new conservative figure. Building a network of supporters, Reagan was elected as governor of California in 1966. During his governorship, he raised taxes, turned the state budget deficit into a surplus, challenged the protesters at UC Berkeley, and ordered in National Guard troops during a period of protest movements.

In November 1979, Reagan announced his candidacy for the Republican nomination in the 1980 presidential election. He won the nomination and the election, defeating incumbent Democratic president Jimmy Carter. At 69 years, 349 days of age at the time of his first inauguration, Reagan was the oldest person to assume the U.S. presidency. Reagan ran for reelection in the 1984 presidential election, in which he was opposed by the Democratic nominee Walter Mondale, who had previously served as vice president under Carter. Reagan defeated him in an electoral landslide, winning the most electoral votes of any U.S. president: 525 (97.6% of the 538 votes in the Electoral College). It was one of the most lopsided presidential elections in U.S. history.Early in his presidency, Reagan began implementing new political and economic initiatives. His supply-side economics policies—dubbed "Reaganomics"—advocated tax reduction, economic deregulation, and reduction in government spending. In his first term, he survived an assassination attempt, spurred the War on Drugs, invaded Grenada, and fought public-sector labor unions. Over his two terms, the economy saw a reduction of inflation from 12.5% to 4.4% and an average real GDP annual growth of 3.6%. Reagan enacted cuts in domestic discretionary spending, cut taxes, and increased military spending, which contributed to a tripling of the federal debt. Foreign affairs dominated his second term, including the bombing of Libya, the Iran–Iraq War, the Iran–Contra affair, and the ongoing Cold War. In a speech in June 1987 at the Brandenburg Gate, four years after he publicly described the Soviet Union as an "evil empire", Reagan challenged Soviet General Secretary Mikhail Gorbachev to open the Berlin Wall. He transitioned Cold War policy from détente to rollback by escalating an arms race with the USSR while engaging in talks with Gorbachev. The talks culminated in the INF Treaty, which shrank both countries' nuclear arsenals.

When Reagan left office in 1989, he held an approval rating of 68%, matching those of Franklin D. Roosevelt and later Bill Clinton as the highest ratings for departing presidents in the modern era. Although he had planned an active post-presidency, Reagan disclosed in November 1994 that he had been diagnosed with Alzheimer's disease earlier that year. His public appearances became more infrequent as the disease progressed. Reagan died at his home in Los Angeles on June 5, 2004. His tenure constituted a realignment toward conservative policies in the United States, and he is often considered a conservative icon. Evaluations of his presidency among historians and the general public place him among the upper tier of American presidents.