Why did US and Israel attack Iran and how long could the war last?

Conflict across the Middle East continues to rage after the US and Israel launched wide-ranging strikes on Iran, killing the country's supreme leader on 28 February.

Iran has responded by launching attacks on Israel and US-allied states in the Gulf.

The fighting escalated quickly, spreading to Lebanon, with casualties and damage mounting on all sides.

When the US and Israel first attacked, they targeted Iran's missile infrastructure, military sites and leadership in the capital, Tehran, and across the country.

Iran's Supreme Leader, Ayatollah Ali Khamenei, who had led the country since 1989, was killed during the first wave of strikes. Israel's military say dozens more senior figures in the powerful Islamic Revolutionary Guard Corps (IRGC) were also killed.

Khamenei's son, Mojtaba Khamenei, was named as his successor on 8 March.

Other high-ranking Iranian officials killed include security chief Ali Larijani, intelligence minister Esmail Khatib and the head of the paramilitary Basij force, Gholamreza Soleimani. Israel says it targeted them in air strikes.

The US and Israel have also targeted key sites linked to Iran's nuclear programme - which Iran insists is entirely peaceful - and Iranian oil and gas sites.

They include Kharg Island, home to a major oil terminal that is considered Iran's economic lifeline.

Israel also targeted South Pars, part of the world's largest natural gas field.

The US-based group Human Rights Activists in Iran (HRANA) reported on 26 March that 3,329 people had been killed in Iran since the war began – including 1,492 civilians, of whom at least 221 were children.

Iran accused the US and Israel of launching an attack on a girls' school near an IRGC base in southern Iran on 28 February, saying 168 people, including around 110 children, were killed.

The US said it was investigating the incident, while Israel said it was "not aware" of any military operations in the area.

Expert video analysis shows a US Tomahawk missile hit a military base near the school, BBC Verify has reported.

Access to Iran for international journalists is limited, and internet connectivity in the country has been almost entirely restricted.

Outside its territory, an Iranian warship was sunk by a US submarine in the Indian Ocean near Sri Lanka on 4 March. At least 87 people were killed.

Iran has described the US and Israeli strikes as "unprovoked, illegal and illegitimate", and has carried out widespread missile and drone attacks in response.

The IRGC said it had targeted Israeli government and military sites in Tel Aviv and elsewhere.

As of 24 March, Israeli authorities said 16 people – all civilians – had been killed by missile fire since the start of the war.

There have also been strikes in countries hosting US bases – Qatar, Bahrain, Jordan, the United Arab Emirates (UAE) and Kuwait – and US-allied Oman and Saudi Arabia.

Thirteen US service members have been killed.

Iran has also been accused of attacking oil and gas facilities, shipping and civilian sites.

At least 20 people have been killed across the Gulf so far, most of them security personnel or foreign workers.

That includes ten people in the UAE and six in Kuwait, while Oman, Saudi Arabia and Bahrain have each reported two deaths.

In northern Iraq, a French soldier was killed by a drone at a Kurdish military base.

On 25 March, seven Iraqi soldiers were killed in an airstrike in Anbar province, in the west of the country, according to a statement from the Iraqi Ministry of Defence. The statement did not say who had carried out the attack.

Also in Iraq, the Popular Mobilization Forces (PMF) - formed in the last decade to fight the Islamic State group - said at least 27 of their members have been killed.

In the Israeli-occupied West Bank, four Palestinian women were killed at a beauty salon in an Iranian missile attack.

Turkey said Nato air defences had shot down three Iranian missiles over its airspace. Azerbaijan accused Iran of attacking an airport with drones.

The US and its Arab allies have condemned Iran's attacks, saying "the targeting of civilians and of countries not engaged in hostilities is reckless".

On 14 March, the Palestinian armed group Hamas in Gaza urged Iran to stop attacking Gulf states, in a rare appeal to its key ally.

On 7 March, Iranian President Masoud Pezeshkian apologised to neighbouring countries that were attacked and said "from now on" the military should not attack neighbouring countries "unless attacked first". But since then, attacks have continued.

Elsewhere, a British military base in Cyprus was struck by a drone, according to the UK Ministry of Defence. Western officials later said the drone had not been launched from Iran.

On 21 March Iran reportedly fired two ballistic missiles at the UK military base on Diego Garcia in the Indian Ocean - but neither missile reached the target.

A new front in the war opened in Lebanon on 2 March when the Iran-backed group Hezbollah fired rockets at Israeli positions, saying it was seeking to avenge Khamenei's assassination.

Israel launched attacks in response, hitting southern and central Beirut and parts of southern and eastern Lebanon.

Israel's defence minister said on 3 March that ground troops would "advance and seize additional strategic areas in Lebanon" in order to stop attacks from Hezbollah.

As of 26 March, Lebanon's health ministry said Israeli attacks had killed 1,116 people, including 121 children.

More than a million people - roughly one in every six in the country - have been displaced from their homes, Lebanon's government said.

The Israeli military also reported three of its soldiers had been killed as of 26 March.

Israeli Defence Minister Israel Katz described the first strikes on Iran as a "pre-emptive" to "remove threats against the state of Israel", although he did not explain why there was a need to take military action at this time.

US Secretary of State Marco Rubio said on 2 March Washington knew there was going to be Israeli action, which meant America had to act "pre-emptively" in the face of expected Iranian attacks on US forces.

But there are also underlying reasons.

Israel and the US – its closest ally – have been arch-foes of Iran since the Islamic revolution in 1979. The Iranian leadership has consistently called for Israel's elimination and denounced the US as its greatest enemy.

The two countries have led Western opposition to Iran's nuclear programme, claiming Iran is seeking to develop a nuclear bomb - something Iran has vehemently denied.

They attacked Iranian nuclear and military sites in June 2025 in a 12-day war.

Since then, they have claimed Iran has been trying to rebuild its nuclear programme and develop missiles capable of delivering nuclear weapons.

Israel considers Iran a threat to its existence and wants the complete removal of Iran's nuclear and missile programme, as well as regime change.

The US first openly talked in January about potentially attacking Iran when its security forces cracked down on protesters with deadly force.

But the US and Iran began negotiations and appeared to be making progress until Trump said he was "not happy" with the way the talks were going on 27 February. Hours later, the US and Israel began attacking.

Instability in the Middle East has begun to impact the global economy.

Iran has been accused of attacking ships in the Gulf, forcing the effective closure of the Strait of Hormuz - a key artery accounting for about 20% of global oil supply.

Trump has postponed his initial threat to strike Iranian power plants and energy infrastructure unless Iran opens the strait, citing what he described as "good" and "productive" talks. Iran, however, has denied any such talks have taken place.

Attacks have been reported on major oil and gas hubs throughout the war. The strikes have prompted some of the world's largest producers of oil and gas to suspend production - leading to a sharp rise in energy prices.

On 24 March, when Trump was asked how hopeful he was a peace deal with Iran would work, he responded that "this war has been won". However, there is little detail on how it could end.

He previously laid out an expansive mission for the war, with the goal to ensure that Iran could not develop weaponry to target the US, Israel or any American allies "for a very long time".

White House press secretary Karoline Leavitt previously suggested the war could last up to six weeks.

Israeli Prime Minister Benjamin Netanyahu said at the start of the war the campaign would "continue as long as it is needed".

The war has prompted one of the most serious disruptions to global travel since the Covid-19 pandemic. Some airlines have carried on operating or have resumed limited flights.

The UK foreign office said anyone planning to travel to the Middle East should check its website for advice relating to their destination.

Reporting by Mallory Moench, Raffi Berg, Emily Atkinson, Olivia Ireland, Robert Greenall, Hafsa Khalil, Gabriela Pomeroy, Jaroslav Lukiv and BBC Persian