US President Donald Trump ordered the assassination of Iran's chief military commander, Major General Qassem Soleimani, the head of the Revolutionary Guard's elite Quds Force on the morning of Friday 3 January.

The event has propelled tensions between the US and the Islamic Republic to new heights and risks the escalation of a major military conflict between the two nations and their respective allies.

While relations between Washington and Tehran have dramatically deteriorated over the past two years, the two nations have been at loggerheads since the early 1950s.

Below is a chronology that maps nearly seven decades of antagonism between the US and Iran:

1953 - The CIA assists plans to topple the democratically-elected Iranian Prime Minister Mohammed Mossadegh, helping to restore the Iranian monarchy by bringing Shah Mohammed Reza Pahlavi to power.

1957 – Washington and Tehran ratify a deal on civil nuclear cooperation.

1967 - The US supplies Iran with a nuclear reactor as well as weapons-grade enriched uranium fuel.

1968 - Iran signs the Nuclear Non-Proliferation Treaty, allowing it to build a civil nuclear program on the agreement that it does not develop nuclear weapons.

1979 – Iranians launch the Islamic Revolution, deposing the US-backed shah's regime, forcing the monarch to flee. Ayatollah Ruhollah Khomeini comes out of exile to be supreme religious guide of the newly created Islamic Republic. Students in Tehran occupy the US Embassy, taking dozens of staff hostage for what would end up being 444 days.

1980 - Washington breaks off diplomatic ties with Tehran, enforcing a far-reaching trade embargo and seizing the Republic's assets. US President Jimmy Carter's plan to rescue hostages fails.

1981 – Minutes after Carter steps down and Ronald Reagan is inaugurated as US president, Tehran releases 52 embassy hostages.

1984 - US puts Iran on list of state sponsors of terrorism.

1986 - Reagan publicly confirms the so-called Iran-Contra affair, a secret arms deal between Washington and Tehran - in contravention of the US embargo - aimed at allowing the US to fund right-wing Contras in Nicaragua.

1988 - US warship Vincennes accidentally shoots down Iran Air Flight 655, killing all 290 passengers.

2002 – Five months after 9/11, US President George W. Bush describes Iran, Iraq, and North Korea as an "axis of evil," popularizing the term as part of the so-called 'War on Terror'. Washington accuses Iran of developing nuclear weapons.

2006 – US says it is willing to take part in multilateral nuclear negotiations with Iran if the Republic halts nuclear enrichment.

2008 - Bush sends first US official since his election to participate directly in nuclear talks with Iran in Switzerland.

2009 – US President Barack Obama says he would extend a hand to Iran if they would "unclench their fist."

2009 – The US, Britain and France report that Tehran is developing a uranium-enrichment site at Fordow near Qom.

2012 - Obama legally allowed to sanction foreign banks if they do not reduce Iranian oil imports. Tehran's oil sales fall, provoking financial slump. Secret talks start over potential nuclear program.

2013 – Iranian President Hassan Rouhani comes to power on a reform platform, pledging to improve global relations.

Obama and Rouhani speak on the phone,  the highest-level contact between the US and Iran in thirty years.

In November, the US and five international powers agree to sign the Joint Plan of Action (JCPOA) nuclear deal, with Iran agreeing to cut back its nuclear program for sanctions relief.

2016 - The US and Iran conduct prisoner swap, including the release of 10 US sailors who were found in Iranian territorial waters.

2018 - US President Donald Trump pulls out of JCPOA nuclear deal in May, reintroducing sanctions against Iran.

2019 – In April, Washington designates the Islamic Revolutionary Guard Corps, part of the Iranian Armed Forces,  a "terrorist organization."

In May, Iran announces it will boost production of enriched uranium in response to the sanctions and the US withdrawing from JCPOA.

In June the US accuses Iran of attacking oil tankers in the Gulf, a claim Tehran denies.

In July a US drone is shot down by Iranian military. Tehran accuses British oil tanker of violating maritime rules and seizes vessel.

In September, drones and missiles attack Saudi Arabia's state-run oil company. The US, alongside many of its Western allies blame Tehran, which denies involvement.

In December, a rocket attack on US military base in Iraq kills a US citizen. Washington accuses an Iraq militia backed by Iran of carrying out the assault and fires on its bases, killing 25 combatants. Protesters rally outside the US Embassy in Baghdad, and break through outer security limits. Trump blames Iran.

In early January, Trump gives go-ahead for assassination of Qassem Soleimani on Iraqi territory.