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

Conflict across the Middle East has entered a fifth day after US and Israeli strikes on Iran, in which the country's supreme leader was killed.

Iran has continued to respond by launching attacks on Israel and US-allied states in the Gulf, which have extended to non-military targets, including civilian sites and energy facilities.

The fighting has escalated quickly, pulling in Cyprus and Lebanon in recent days, with casualties and damage mounting on all sides.

The US and Israel launched widespread strikes on 28 February, targeting Iran's missile infrastructure, military sites and leadership in the capital, Tehran, and across the country.

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

Since the weekend, the US and Israel have continued to target key sites. Israel said that included a covert nuclear compound. Iran has repeatedly insisted its nuclear programme is entirely peaceful.

The death toll in Iran since the US-Israeli attacks began has reached 787, according to the Iranian Red Crescent. Meanwhile, US-based Human Rights Activists in Iran (HRANA) reports that 1,097 civilians have died, including 181 children.

Iran accused the US and Israel of launching an attack on a girls' school near an IRGC base in southern Iran on Saturday, saying more than 160 people were killed.

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

Internet connectivity in Iran has been almost entirely restricted and its airspace has been closed.

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.

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

Drones hit the US embassy in Saudi Arabia's capital Riyadh, and a drone also hit a car park adjacent to the US consulate in Dubai.

Iran has been accused of widening its attacks to include other targets in recent days, on shipping and civilian sites - including hotels in Dubai.

The US and its Arab allies issued a joint statement condemning Iran's attacks, saying "the targeting of civilians and of countries not engaged in hostilities is reckless and destabilising behaviour".

Elsewhere, a British military base in Cyprus was struck by a drone, according to the UK Ministry of Defence, which the Cypriot president blamed on Iran.

Six US servicemen have been killed and 18 injured in action as of Monday, according to Centcom.

Israeli Defence Minister Israel Katz described the attacks on Saturday as a "pre-emptive strike" 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 Monday the US knew there was going to be Israeli action, which meant America had to act "pre-emptively" in the face of expected Iranian attacks on American forces.

Israel Defense Forces (IDF) spokesman Brig Gen Effie Defrin revealed that the military operation was preceded by months of strategic deception that caught Iran off guard.

In the US, some lawmakers have called for President Donald Trump's administration to provide evidence that Iran posed a threat before Washington went to war.

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 war which lasted for 12 days.

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

Trump said these missiles could eventually reach the US, though this has not been supported by US intelligence assessments.

For its part, 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. Hours later the US and Israel began attacking.

A new front in the war opened in Lebanon on Monday when the militant group Hezbollah fired rockets at Israeli positions.

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

Hezbollah is allied to Iran's government and said it was seeking to avenge Khamenei's assassination.

In Israel, the defence minister said on Tuesday ground troops would "advance and seize additional strategic areas in Lebanon" in order to stop attacks from Hezbollah.

The United Nations said more than 30,000 people had been forced to flee their homes since the escalation of hostilities.

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 and gas supply.

Attacks have also been reported on major oil and gas hubs, including in Oman's Duqm commercial port and the UAE's Fujairah terminal.

The strikes have prompted some of the world's largest producers of oil and gas to suspend production, including Qatar's liquefied natural gas (LNG) facilities and Saudi Arabia's largest domestic refinery.

Oil and gas prices have surged, with the Brent benchmark oil price hitting $83.96 (£62.70) a barrel on Wednesday, a rise of 15% since Saturday.

President Trump said on Tuesday that the US navy would protect ships in the region "if necessary" and "at a very reasonable price" in a bid to stop global energy supply issues.

Iran has said it will appoint a new supreme leader swiftly.

A transitional leadership council has been formed to run the country temporarily, consisting of: President Masoud Pezeshkian, judiciary chief Gholamhossein Mohseni Ejei and senior cleric Alireza Arafi.

The formal selection of a successor to Khamenei is carried out by 88 senior clerics, known as the Assembly of Experts.

Under the country's constitution, these clerics must appoint the new supreme leader as soon as possible, but this may prove difficult while the country is under attack.

The IRGC has already named a new commander-in-chief, Ahmad Vahidi.

Two days after the attacks began, Trump said military action was projected to last for "four to five weeks, but we have capability to go far longer than that".

On the first day, Israeli Prime Minister Benjamin Netanyahu said 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, with widespread airspace closures and thousands of flights grounded across the Middle East.

Carriers including Emirates and Etihad have been able to fly a limited number of repatriation flights out of Dubai and Abu Dhabi to the UK and other European countries. Commercial flights remain suspended.

Flights out of Qatar also remain suspended due to the closure of airspace in the region.

The UK government is due to fly a chartered plane from Muscat in Oman, around 280 miles (451km) from Dubai, back to Britain to bring some stranded nationals home.

The UK Foreign, Commonwealth and Development Office (FCDO) said anyone planning to travel to the Middle East should check its website for advice relating to their destination.

With additional reporting by Olivia Ireland, Robert Greenall, Hafsa Khalil, Gabriela Pomeroy and BBC Persian.