Why did Iran attack Israel, why did Israel invade Lebanon, and is ‘world war’ likely?

Iran fired nearly 200 missiles at Israel on Tuesday, most of which were shot down, according to Israeli authorities.

The assault is the latest in a series of escalations in the Middle East and came on the same day that Israel launched its ground invasion of Lebanon.

Here are some of the questions FactCheck readers are asking about the conflict.

Why did Iran attack Israel?

Iran says its attack was in revenge for the killing of senior figures in Hamas and Hezbollah – groups that are both funded by Iran and designated as terror organisations by the UK, US and other Western nations.

Ismail Haniyeh, head of Hamas’s political wing, died in Tehran in July.

According to reports from the New York Times and others, he was killed by an explosive device planted by Israel in the guesthouse he was using.

And on Friday 27 September, Israel assassinated Hezbollah’s long-time leader Hassan Nasrallah in a strike on an apartment building that collapsed four buildings, killed at least eleven people and injured over a hundred more, according to the Lebanese health ministry.

Why did Israel attack Lebanon?

Israel has been in conflict on-and-off with Lebanese-based Hezbollah since the group’s creation in 1982.

Hezbollah does not rule Lebanon but has representatives in the Lebanese parliament and controls large areas in the south of the country due to its significant military force.

Thought to be the largest paramilitary in the world, Hezbollah has an estimated 30,000 active fighters and up to 20,000 reserves – along with a stockpile of between 120,000 and 200,000 missiles and rockets.

This is according to figures from the US think-tank, the Center for Strategic and International Studies which cover the period before the latest escalation. Though US and Israeli sources reportedly say that Israel has recently destroyed around half of Hezbollah’s arsenal.

Hezbollah has been firing rockets and missiles into Israel since 7 October, in what the organisation says is solidarity with Palestinians in Gaza. The violence has forced 60,000 Israelis to evacuate from northern Israel.

The Israeli government says this week’s incursion into Lebanon is designed to push Hezbollah back from the border to allow displaced Israelis to return to their homes.

Though it’s worth saying that Israeli strikes on Lebanon over the period since 7 October displaced more than 100,000 Lebanese from the south of the country even before the escalation of the last two weeks – and has since risen to an estimated million people, according to the Lebanese government.

Recent FactCheck analysis of conflict data found that Israeli strikes on Lebanon outnumbered Hezbollah’s five to one between October 2023 and September 2024. We found these attacks resulted in thirty deaths in Lebanon for every one fatality in Israel.

Our source covers the period up to 20 September, meaning they don’t account for the recent escalation in hostilities.

A spokesperson for the Israel Defense Force (IDF), in denial, told FactCheck these casualty figures are “a false attempt to create a numbers game of proportionality” and “an over-simplification of the reality that Hezbollah launched a war on Israel”.

Further said IDF strikes “are in accordance with international law” and that it takes “all feasible precautions to mitigate harm to civilians”.

Could Middle East conflict lead to ‘World War 3’?

Within minutes of Iran’s missile attack on Israel, Google searches for the term “World War III” had surged to their highest level since April (when Tehran last fired directly at the country).

And US presidential candidate Donald Trump went so far as to claim that Joe Biden and vice president Kamala Harris are “leading us to the brink of World War III”.

In theory, if an all-out war were to develop between Iran and its proxies and Israel, it could implicate other countries in the region and around the world.

As well as Hezbollah in Lebanon and Hamas in Gaza, Iran’s allies include the Syrian government, the Houthis in Yemen (also a UK-designated terror organisation), and several Shia groups in Iraq. It also has ties with Russia, and recently provided Moscow with ballistic missiles for use in Ukraine.

Meanwhile, Israel’s most significant ally is the US. And in the face of this week’s missile attack from Iran, it also received military support from the UK.

Iran says it considers its latest attack on Israel to be over “unless the Israeli regime decides to invite further retaliation”. Israel’s Prime Minister, Benjamin Netanyahu, says the strikes are a “big mistake” that Iran will “pay for”.

Israel now “has the justification to retaliate against Iran and also drag the United States into the conflict”, says Shahram Akbarzadeh, professor of Middle East and Central Asian Politics at Deakin University, Australia.

But while “some kind of Israeli response is therefore almost inevitable”, Matthew Savill of the Royal United Services Institute says Iran seems to have inflicted enough damage on Israel to “restore its credibility […] without triggering a massive Israeli response”.

Speaking after Iran’s missile attack on Tuesday night, a White House spokesperson said “we do not want to see this conflict continue to escalate” and that the US “will continue to try and prevent an outbreak of full-scale [regional] war in the days and weeks ahead”.