US-Iran relations timeline: 7 major events since the Iranian Revolution

American-Iranian relations have been fraught with difficulties and mutual animosity since the 1979 Iranian Revolution and subsequent hostage crisis.

Friday's phone conversation between the newly-elected Iranian President Hassan Rouhani and US President Barack Obama is the first high-level contact between the two nations in more than 30 years.

Though it is too early to tell if the conversation marks a breakthrough in both US-Iranian relations and in the talks over Iranian nuclear weapons, it was a historic moment.

Here are seven other events since 1979 that have defined the recent relationship between the two countries:

1979: The Iranian Revolution

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The US-backed Shah is forced to flee the country after massive protests oust him from power. His exit sees the overthrow of the regime and the return of the religious leader Ayatollah Khomeini from exile in February of that year. Vocally anti-American and anti-Western, Khomeini calls for the expulsion of all foreigners from the country.

1979: The Hostage Crisis and oil ban

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In November, young Iranian militants storm the US embassy and take 63 Americans hostage with the support of the Ayatollah. The hostage crisis effectively ends US-Iranian relations and sees a botched rescue attempt by US commandos. President Jimmy Carter's re-election prospects are hurt badly by the failed rescue. During the crisis, President Carter bans the import of Iranian oil – a prohibition which continues to this day. The hostages are finally freed after 444 days.

1986: The Iran Contra Scandal

The United States held secret talks with Iran in order to free their hostages in Lebanon in exchange for weapons' sales during the Iran-Iraq War. The profits of those sales were channeled by the US to Nicaraguan rebels known as contras. The revelations were exposed and caused a scandal during the presidency of Ronald Reagan. The incident led to a series of resignations and an investigation by Congress.

1987: US involvement in the Iran-Iraq War

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The United States entered the brutal conflict in 1987 in an effort to protect shipping lanes, before becoming further embroiled in the fighting. The US did not fully take sides but eventually extended various forms of aid to Iraq, which led the conflict into a stalemate. It was recently reported that the US was said to have been aware of the chemical weapons used by Iraqi soldiers on Iran before the attack occurred, but did nothing to stop it. The US also attacked Iranian oil platforms in the Gulf after one of its ships were destroyed by a mine, as well as shooting down an Iran Air passenger plane, which it alleges was an accident.

2003: Iranian nuclear facilities discovered

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Though publicly revealed in 2002, the IAEA did not outline Iran's breaches of nuclear agreements until a 2004 report, which prompted first the European Union, and then the United States, to pursue talks and further sanctions against the Iranian regime. The IAEA has monitored the development of Iran's alleged nuclear weapons program in quarterly reports ever since, tracking their development and condemning their breaches of the Nuclear Non-Proliferation Treaty.

2003-present: Nuclear negotiations

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Nuclear negotiations with Iran and the Western powers have been stalled since the P5+1 negotiations in Baghdad last year. The negotatioins have started and stopped a number of times with Iran continuing its enrichment of uranium and building new uranium enrichment facilities despite calls for it to halt its work. Though recently the United States has called for bilateral talks, it has tended to negotiate under the auspices of the P5+1.

2013: Obama-Rouhani phone call

In a sign of the times Iranian President Rouhani tweeted that he had spoken to the American president by phone on Friday, September 27. The conversation occurred as Rouhani was leaving New York after the UN General Assembly and last 15 minutes. The two then exchanged messages on Twitter. The last time a US president spoke with an Iranian leader was in 1979, when Jimmy Carter spoke to Shah Mohammed Reza Pahlavi by phone just prior to his ouster.