United States-Iran tensions have surged to the highest point in decades after President Donald Trump on Sunday ordered direct strikes that he said “obliterated” key nuclear facilities across the Middle Eastern country.

Iran remains the biggest adversary of the US in the region since the 1979 Islamic revolution led by Ayatollah Ruhollah Khomeini toppled pro-Western Mohammad Reza Pahlavi. Since then, the two nations have sparred over a multitude of issues, including Iran’s nuclear ambitions, Iran’s backing of proxies in the region, and US political interference.

Israel, which has long considered Iran a threat, launched unprecedented strikes across Iran last week after accusing the country of developing nuclear weapons. Israeli claims have not been backed by any credible proof, but Trump dragged the US into the war following the Israeli strikes.

On Sunday, the US directly hit Iran in what the Trump administration called a highly sophisticated covert attack that involved more than 125 US aircraft and 75 precision bombs. Washington said it “devastated” Iran’s nuclear sites, but Tehran has warned it will retaliate.

Here’s a timeline of US-Iran relations since 1953:

• (1953) US-backed coup and reinstallation of the shah: Tensions initially began brewing over the democratically elected Iranian Prime Minister Mohammad Mosaddegh’s efforts to nationalise the Anglo-Iranian Oil Company (now BP). The British colonial power controlled the majority stake in the joint-venture company since oil was discovered in the early 1900s. Mosaddegh’s moves to nationalise the company after his 1951 election angered the British. The US’s Central Intelligence Agency supported the United Kingdom in engineering a coup and backing once-deposed monarch, Pahlavi, back into power as shah.
• (1957) Atoms for Peace: The shah’s ambitions for a nuclear-powered Iran gained support from the US and other Western allies. Both countries signed a nuclear agreement for the civilian use of nuclear power as part of then-US President Dwight D Eisenhower’s Atoms for Peace programme. A decade later, the US provided Iran with a nuclear reactor and uranium to fuel it. The nuclear collaboration forms the basis for the current nuclear question.
• (1979) Islamic revolution: While relations between Tehran and Washington flourished, Iranians groaned under the dictatorship of the shah and resisted the perceived overreach of Western influence on their business. Revolutionary protests began rocking the country in late 1978 and forced the shah to flee in January 1979. Exiled Islamic scholar Ayatollah Ruhollah Khomeini returned to rule the new Islamic republic.
• (1980) US cuts diplomatic ties: Following the US’s move to admit the shah for cancer treatment after his exile, Iranian students broke into the US embassy in Tehran and kidnapped 52 Americans for 444 days. Washington cut off diplomatic ties and imposed sanctions on the country. The shah died in exile.
• (1980-88) US backs Iraqi invasion: Following Iraq’s invasion of Iran under Saddam Hussein, who was eager to push back against Khomeini’s ideology, the US sided with Iraq, deepening tensions between the two nations. The war lasted till 1988 and saw thousands die on both sides. Iraq also used chemical weapons on Iran.
• (1984) Sponsor of terror designation: President Ronald Reagan officially designated Iran as a “state sponsor of terror” after a series of attacks in Lebanon, where the US had been drawn in after Israel invaded the country. In one attack on a military base in Beirut, 241 US service members were killed. The US blamed Hezbollah, a Lebanese Shia movement backed by Iran. Later, though, Reagan worked with Iran behind the scenes to free American hostages held by Hezbollah. When it came to light, the Iran-Contra affair, as it was termed, was a huge scandal for Reagan.
• (1988) Iran Air flight shot down: Amid war tensions and even direct attacks on each other’s military warships in the Gulf, a US naval ship breached Iranian waters and fired at the civilian Iran Air flight (IR655) headed to Dubai on July 8. All 290 people on board were killed. The US, which claimed it was a mistake, did not formally apologise or claim responsibility but paid families $61.8m as compensation.
• (1995) Tighter sanctions: Between 1995 and 1996, the US imposed more sanctions. Then, President Bill Clinton’s executive orders banned US companies from dealing with Iran, while Congress passed a law penalising foreign entities investing in the country’s energy sector or selling Iran advanced weapons. The US cited nuclear advancement and support of groups like Hezbollah, Hamas, and Palestinian Islamic Jihad.
• (2002) 9/11 aftermath: Following the 9/11 attacks on the US, President George W Bush, in a State of the Union address, said Iran was part of an “Axis of Evil” alongside Iraq and North Korea. At the time, Iran had been parlaying with the US behind the scenes to target their mutual foes – the Taliban in Afghanistan and al-Qaeda. The cooperation was soured, and by the end of 2022, international observers noted highly enriched uranium in Iran, inviting more sanctions.
• (2013) Iran nuclear deal: Between 2013 and 2015, US President Barack Obama began high-level talks with Iran. In 2015, Tehran agreed to the nuclear deal, formally known as the Joint Comprehensive Plan of Action (JCPOA), that would limit Iran’s nuclear activities in exchange for an easing of sanctions. China, Russia, France, Germany, the UK and the European Union were also party to the deal that capped Iran’s enrichment at 3.67 percent.
• (2018) Trump withdraws from the nuclear deal: Under Trump’s first term, the US unilaterally withdrew from the deal in 2018 and slapped back sanctions against Iran. Trump and Israel had been critical of the deal. Iran also called off its commitments and began producing enriched uranium beyond the limits the deal had imposed.
• (2020) IRGC leader assassinated: During Trump’s first term, the US killed Iranian General Qassem Soleimani, the head of the elite Quds Force of Iran’s Islamic Revolutionary Guard Corps (IRGC), in Baghdad in a drone strike. A year earlier, the administration had named the Quds Force a “terrorist” organisation. Iran responded with strikes on US assets in Iraq.
• (2025) Letter to Tehran: In March, Trump shot off a letter to Iran’s Supreme Leader Ayatollah Ali Khamenei proposing new negotiations on a nuclear deal with a deadline of 60 days. But Khamenei rejected the offer, saying the US is not seeking negotiations with Iran but rather imposing demands on it. Talks started unofficially in Oman and Italy, with Muscat acting as the mediator. Trump claimed his team was “very close” to a deal after several rounds of talks and warned Israel against strikes. Tehran, too, expressed optimism but insisted on the right to enrich uranium – a sticking point in the talks. Israel launched strikes across Iran a day before the sixth round of the Iran-US talks.
• (2025) US strikes: The US bombed three key nuclear facilities in Iran, citing security concerns and the defence of Israel.