The Iranian army returned to its barracks, apparently accepting that the supporters of the Islamic leader Ayatollah Khomeini were in power.
It was a remarkable end to a turbulent fortnight that has since been called the Iranian or Islamic revolution.
The aftermath of that short period created diplomatic fault lines that continue to this day, forcing two countries onto irremediably opposite sides, to the extent that they are now, not just literally, continents apart.
The depth of the animosity rears its head regularly.
In 2018, Donald Trump pulled out of an anti-nuclear deal backed by the EU, China and Russia, aimed at stopping Iran develop ballistic weapons. Since then, he has since decried his own spies’ assessment that Iran is not an “immediate” threat.
His actions are emblematic of the antagonistic sentiment felt by Washington towards Tehran and, reflective of the Iranian regime’s regular reference to the US as the “great Satan”.
But, what happened to cause such deep division between the US and Iran?
The origins of the rift between the US and Iran go back beyond the revolution. Many of Iran’s gripes concern foreign efforts to manipulate its pre-1979 leaders, including the country’s Shah, the name for its king.
In the Second World War, America was involved in a UK/Soviet effort to keep oil flowing to the Allies from Iran and maintained close links with the country’s ruler as the Cold War got under way, afraid of Soviet ambitions in the region.
In 1953, fearful of a communist takeover and restrictions in oil shipments, the CIA joined Britain’s MI6 in orchestrating a coup to remove prime minister Mohammad Mosaddegh, a man many Iranians regard as a hero for resisting foreign domination.
It was an age in which the US and other Western nations were paranoid about the risks posed to their way of life by the advance of communism and expansion of the Soviet bloc.
In the years following the coup, the US kept Iran close in order to act as a bulwark against Soviet ambitions, providing aid and, some say, training for the Shah’s secret police, SAVAK.
This, according to ex-CIA Iranian field officer William Daughty, left “many Iranians more convinced than ever that the Shah and their country were simply a dominion of the United States, administered by or through the CIA”.
Among those angry at the relationship between the Shah and the US was a conservative religious leader called Ayatollah Ruhollah Khomeini, who ended up being forced into exile over his views.
In the 1970s, a series of actions by the Shah and mismanaged worldwide economic events conspired to make his regime increasingly unpopular.
There was growing resentment at the king’s tenuous right to rule (his family was dubiously awarded the throne in the 1920s).
In the increasingly febrile atmosphere, the role of SAVAK, which is also said to have had Israeli help to set up, became increasingly in focus.
Meanwhile, despite living in Iraq and later Paris, Khomeini had become increasingly influential by outlining his vision for ditching the shahs and ruling Iran by Islamic doctrine.
While many of his ideas were laid out in books, copies of his sermons were bootlegged on cassette tapes and sold in their thousands in markets to ordinary Iranians, spreading his ideology widely.
In 1978, discontent turned into protests, with many supporters of Khomeini in the vanguard. These were met with stiff resistance, with the deaths of demonstrators only adding fuel to the fire.
Increasing numbers of people were being killed during clashes, which involved students who supported a range of anti-government causes as well as Khomeini, and as the year went on strikes were called in reaction to martial law.
In response, the Shah tried to appoint a new government while the army, which was called on to resist the protests, appeared to prevaricate as many of its rank and file supported the opposition.
In January 1979, with the security situation deteriorating day by day, the Shah handed power to a new prime minister and fled with his family to Egypt, for a new life in exile.
On 1 February, Ayatollah Khomeini sensed the moment was right and returned to Tehran to be met by crowds of millions of people.
The interim prime minister, Shahpour Bakhtiar, had hoped to strike an alliance with the cleric but it was clear where the real power lay, and Khomeini announced he would be the one to “appoint the government”.
Within days, Iranian radio was reporting Bakhtiar was missing after his house had been burned down, fire stations were occupied and police officers had been forced to flee as Khomeini’s supporters grabbed control.
Many soldiers deserted, leaving tanks abandoned. The only remaining resistance came from Imperial Guard troops, loyal to the newly absent Shah. But that soon crumbled too, leaving the revolution complete, with more than 200 dead.
Two months after seizing power on a wave of popular support, Ayatollah Khomeini declared an Islamic republic.
It was the world’s first – a modern nation state, with a democratically elected government, underpinned by an unelected Islamic theocracy.
Many of the disparate groups who had taken part in the popular revolutions had been optimistic they would have a place in the new hierarchy. But, within months, it was made clear who was in charge.
The US had been hopeful of good relations between its State Department and the new Islamic government. Secret files declassified in the last few years show considerable contact between diplomats and Khomeini’s team, including himself, before he left Paris for Tehran.
But, within days of the revolution being over, the administration of Jimmy Carter, which had admitted the Shah into the US for cancer treatment, began to realise there may be problems ahead.
The US embassy was vandalised on 14 February, and the following November a group of students seized the building and took its 66 occupants hostage.
One of the leaders read out a statement, saying: “We Muslim students, followers of Imam Khomeini, have occupied the espionage embassy of America in protest… We announce our protest against America for granting asylum and employing the criminal Shah while it has on its hands the blood of tens of thousands of women and men in this country.”
The takeover was backed by Khomeini, promoting Carter to put pressure on the new regime by freezing Iranian assets.
In response, the Ayatollah unleashed a furious tirade of vitriol to his amassed followers, declaring: “Don’t forget that the US is your worst enemy. Don’t forget to chant: ‘Death to US’.”
Amid the revolutionary fervour, there was no appetite in Iran for negotiation and in the end, 52 American diplomats were held for 444 days, with a failed rescue mission along the way resulting in the deaths of eight servicemen.
The US broke off diplomatic relations with Iran in 1980 and has never restored them.
While US diplomats were still being held hostage in Tehran, in September 1980, Iraqi forces invaded Iran, citing Iran’s failure to abide by a border agreement. By 1982, Iran had hit back, retaking the territory Iraq had initially seized and pushing on towards the Iraqi city of Basra.
The US, terrified the Iranians might defeat Iraq and move on to seize other Middle Eastern oil rich allies, began supporting the regime of Saddam Hussein and arranged for non-US-made weapons to be imported, according to several sources.
At the start of the Iranian revolution, the US had held up a shipment of weapons the Shah’s regime had paid for, causing further rancour among his successors.
In 1983, two separate attacks against the US embassy and a US Marine peacekeeper barracks in Beirut killed a total of 362 people, while another attack on a French base killed 58 troops. The attacks were claimed by a previously unknown Shia Islamist group called the Islamic Jihad Organisation, but many sources have accused Iran of being behind them.
Five years later, after the US stationed its navy in the Persian Gulf to protect shipping from the ongoing Iran-Iraq war, an Iran Air passenger jet was shot down over Iranian territorial waters by a surface-to-air missile fired by the USS Vincennes in the Straits of Hormuz.
The US said later the US navy ship had incorrectly believed the aircraft was an attacking war plane, but never apologised. Iran accused the US of being negligent.
The same year, in 1988, Pan Am Flight 103 was blown out of the sky above Lockerbie, Scotland, an act of terror some have blamed on Iran.
Despite the deteriorating relations between the two countries, there were moments when it appeared as though they were able to co-operate, albeit in controversial circumstances.
Evidence emerged in 1986 that a faction of the Reagan administration had arranged to ship replacement weapon parts to Iran, despite a US-sponsored arms embargo, in exchange for Iran’s help in getting US hostages being held in Lebanon released.
The hostages were being held by a Shia militant group called the Islamic Jihad Organisation, which was allied to Hezbollah and arose out of the conflict in southern Lebanon.
The US had designated Iran a State Sponsor of Terrorism in 1984, originally for its support for Hezbollah and other militant groups and later for its support of Hamas. Both Hezbollah and Hamas are designated terrorist groups by several nations, including the UK.
Since then, with continued US support for Israel, it has accused Iran of continuing to aid Hezbollah and Hamas in their attacks on Israelis.
Iran has responded by denying involvement in “plots”, and has accused Western nations, including the US, of supporting groups or people it regards as terrorists, including Saddam Hussein.
Bill Clinton went further than Reagan, naming Iran a “rogue state”.
George W Bush upped the rhetoric even more by listing Iran as part of an “axis of evil”, states which not only sponsored terrorism but also sought weapons of mass destruction.
US evidence for an Iranian nuclear programme was said to have come from defectors, satellite images and later from drone surveillance.
As the row over the country’ nuclear activities ramped up, with numerous sanctions placed on Iranian activities, its president Mahmoud Ahmadinejad called Iran’s accusers “mentally retarded”.
It was not until the Joint Comprehensive Plan of Action was concluded in July 2015, that tensions began to briefly ease.
Now, relations have never been worse.
Recent polls have illustrated the extent relations have consistently deteriorated among their populations.
A BBC World Service polls found in 2013 that 87% of Americans view Iran mainly negatively. A poll in 2018 carried out by a division of Canadian group People Analytics found that 81% of Iranians had a very or somewhat unfavourable view of the US.