General Qasem Soleimani, the head of Iran's elite Quds force and mastermind of its regional security strategy, was killed in a US airstrike at Bagdad airport on Friday after months of rising tensions between the US and Iran.
US president Donald Trump ordered the drone strike and Secretary of State Mike Pompeo said the operation disrupted an "imminent attack" in the region that put American lives at risk.
Iran's leader Ayatollah Khomeinei promised "harsh vengeance" in response to the attack, prompting speculation about what might happen next and raising the stakes of a conflict between the two nations.
Here, we look at the events leading up to the general's killing, stemming from Mr Trump's decision to withdraw from the 2015 nuclear deal and restore crippling sanctions.
Timeline leading to the US killing of Iranian general Qasem Soleimani
July 25, 2015: The US, Iran and other world powers including the UK announce an agreement they describe as a “first step” towards preventing Iran from obtaining nuclear weapons.
October 2016: Presidential candidate Donald Trump says he will withdraw the US from the deal if elected.
May 8, 2018: President Trump announces the US will withdraw from the Iran deal. Iran, Britain, France and Germany say they will maintain the pact.
August - November 2018: The US reimposes economic sanctions on Iran, targeting oil, shipping, banking and other sectors.
April 8, 2019: Mr Trump says he will designate Iran’s Islamic Revolutionary Guards as a foreign terrorist organisation, despite opposition from the US military.
April 22, 2019 : The US says it will end exemptions on sanctions against countries buying oil from Iran.
May 8, 2019: Iran announces it will increase its production of enriched uranium.
May 12, 2019: Two oil tankers from Saudi Arabia, and one each from the United Arab Emirates and Norway are attacked in the Persian Gulf. The US blames Iran.
June 20, 2019: Iran shoots down a US drone it says violated its airspace, which America denies. Mr Trump orders attacks against Iran but cancels them shortly before they were to be launched.
July 1, 2019: Iran says it has exceeded the amount of low-enriched uranium it was allowed to produce under the 2015 agreement.
July 4, 2019: British marines seize the Iranian oil tanker Grace 1 in Gibraltar at the request of the US.
July 18, 2019: Mr Trump says the US navy shot down an Iranian drone that came close to the ship.
July 20, 2019: Iran seizes the British-owned oil tanker Stena Impero near the Strait of Hormuz.
July 22, 2019: Iran arrests 17 of its citizens and charges them with spying for the US. Some were reportedly executed.
December 27, 2019: An American civilian contractor is killed and several troops injured in a rocket attack in the Iraqi city of Kirkuk. Kataib Hezbollah, an Iran-backed militia group, is blamed.
December 29, 2019: The US bombs three sites in Iraq and two in Syria which are linked to Kataib Hezbollah, killing 25 people.
December 31, 2019: Protesters attack the US embassy in Baghdad.
January 2, 2020: Iranian military leader Qasem Soleimani and five others are killed in a US drone strike at Baghdad airport.
