Here is a recap:

- Terror blacklist -

On April 8, 2019 Washington declares Iran's elite Revolutionary Guard Corps a "terrorist" group. Its Quds Force, which operates abroad, is also put on the blacklist.

- Nuclear accord unravels -

On May 8, a year after Washington unilaterally withdrew from an international 2015 deal curbing Iran's nuclear programme and reimposed sanctions, Tehran warns it is prepared to resume nuclear activity.

- US drone shot down -

Iran's Revolutionary Guards say on June 20 they shot down a US drone which violated Iranian airspace near the Strait of Hormuz.

Trump approves a retaliatory strike, but cancels it at the last minute.

On June 24, Trump announces "hard-hitting" financial sanctions on Iran's supreme leader Ayatollah Ali Khamenei and senior Iranian military leaders.

On July 18, Trump says the US military has taken down an Iranian drone that came dangerously close to one of its naval vessels in the Strait of Hormuz.

- Saudi oil attack -

On September 14, aerial attacks claimed by Yemen's Iran-backed Huthi rebels spark fires at two major Saudi oil facilities.

Tehran is accused by the United States and other powers of being responsible but denies involvement.

On September 20, Trump announces "the highest sanctions ever imposed on a country", hitting Iran's central bank.

- US strike kills commander -

On January 3, 2020 a US strike kills top Iranian commander Qasem Soleimani, the Quds Force commander, in Iraq.

The killing comes days after thousands of pro-Iranian supporters stormed the US embassy in Baghdad, chanting "Death to America!", angered by US strikes against Hashed bases in Iraq.

Those US strikes, on December 29, had been in retaliation for rocket attacks against US interests in Iraq in which a US civilian contractor was killed.

- Nuclear deal unravels further -

On January 5, Iran announces its fifth step back from the nuclear deal with world powers agreed in 2015, saying it will forgo a "limit on the number of centrifuges".

- Iran missiles -

Iran launches a volley of missiles at Iraqi bases housing US and other coalition troops on January 8, which Khamenei calls a "slap in the face" for the US. There are no casualties.

- Iran 'error' downs plane -

The same day, a Ukrainian passenger jet slams into a field shortly after taking off from Tehran, killing all 176 people on board.

On January 11, Iran's President Hassan Rouhani says a military probe found that "missiles fired due to human error" caused Iran's worst civil aviation disaster since 1988, calling it an "unforgivable mistake".

"Human error at time of crisis caused by US adventurism led to disaster," tweets Iranian Foreign Minister Mohammad Javad Zarif.