How the Gaza war may escalate internationally

Israel-Hamas forecasting part 2

How the Gaza war may escalate internationally
Illustration by Laurel Molly, © All Rights Reserved

Overview of the next six months:

  • 21% chance Israel launches a major missile or aerial attack on Iran
  • 9% chance of a lethal confrontation between the US and Iran
  • 18% chance that Europe sees rioting at the level of the 2011 London riots or greater

On Friday, we published the first part of our analysis on the Israel–Hamas war. We covered three key questions related to the escalating conflict between Israel and Hamas in Gaza: Hamas losing control of Gaza City, the potential death toll in Gaza, and the prospect of wider fighting with Hezbollah.

Across the board, the outlook of the forecasters suggests the next six months will bring about changes to the region of a magnitude not seen for decades. But, alongside these changes, what might the effects be beyond the Levantine region?

Israel is yet to launch its ground invasion into Gaza, and Swift Centre forecasters believe the chances of serious international escalation are significant. We examine three additional questions focused on how the crisis may escalate globally over the next six months: the chances of retaliatory strikes by Israel against Iran, a fatal confrontation between the US and Iran, and the possibility of severe riots in Europe linked to the conflict.

Events might lead Israel to launch a major attack on Iran

Beyond those that border Israel, the nation state most present in the minds of international observers is Iran. Iran has long provided funding and support to militant groups like Hamas, Hezbollah, and the Sabireen Movement. While Hamas, a Sunni group, is not a natural ally of Shia-majority Iran, their shared opposition to Israel has led to Iranian funding and weaponry support. Hezbollah, on the other hand, has been under the aegis of Iran since its inception, functioning as its primary proxy in the region. Operating in Lebanon as a Shiite political party and militant group, it has long opposed Israel and the Western influence on the Middle East.

On Thursday, Israel conducted airstrikes on the Aleppo and Damascus airports, which reportedly serve as transit points for Iranian arms sent to Hezbollah, as well as for civilian travel. While appearing escalatory, Israel has carried out attacks on Iran-linked targets in Syria multiple times before this. The question that our forecasters are left wondering is whether Israel will go further and launch a major attack against Iran directly.

They chose to forecast specifically on whether they will launch a missile or aerial attack on Iran in the next six months, defining a 'major attack' as one involving three or more missile or aerial strikes on either military sites (killing at least 5 military personell), economic targets (such as oil production, refineries, or ports), key nuclear sites, or other significant targets such as major government buildings. (Attacks that merely target and eliminate a few operatives on the ground would not be considered 'major').

Under this definition, the forecasters assigned a 21% chance to such an attack in the next six months. A reason why this might be considered unlikely is recent Israeli and American restraint in blaming Iran for Hamas' attack, as highlighted by one forecaster:

The United States and Israel have so far refrained from drawing a direct link between Iran and the Hamas attack. The WSJ published an article claiming that Iran was intimately involved, though the lead journalist who wrote the WSJ article has been accused by her former boss at Reuters of fabricating stories and some are doubtful that the newspaper could have quickly pieced together things that Israeli and Western intelligence apparently missed. Either way, it seems that Israel isn't in a hurry to directly implicate Iran, though its Ambassdor to the US did say that Iran is always behind Hamas (which isn't too dissimilar from the US statements about Iran's general support for Hamas). The Washington Post also published an article quoting one analyst claiming a direct link, but didn't include anything concrete. More may come to light, though.

Another, assigning 10% to this, explains why they believe this is unlikely:

If war with Lebanon hasn't fully broken out yet, an attack on Iran will largely guarantee it will, so Israel has a strong reason not to do it. If war with Lebanon has fully broken out, Israel will not be in the mood to commit precious resources to a largely symbolic strike. Add to this the practical difficulties of such a strike (like crossing Iraqi airspace) and it looks fairly unlikely to me.

The reason the group aggregate remains relatively high is down to the many possible routes of escalation. One forecaster says "Israel is currently emboldened to put an end to Hamas and its sponsors, both domestically and abroad, such that a missile launch is significantly more likely than the base rate". However, several assert that it mostly depends on what Iran decides to do next.

Iran's next actions

Reports from the Axios news site highlighted that Iran has informed Israel via the UN of its intent to intervene in the Gaza campaign, especially if they go ahead with a ground offensive. Iranian Foreign Minister, Hossein Amir-Abdollahian, emphasized that this could result in a significant setback for Israel, likening it to “a huge earthquake”.

If Hezbollah enters the war, which forecasters think is a realistic possibility, most viewed direct retaliation against Iran as more likely. Additionally, forecasters said that if Iran decides accelerate their nuclear weapons program, Israel will attack to try and stop them. Another forecaster provided the details for why Israel might respond in haste:

Earlier this year, American officials estimated that Iran can make the fissile material necessary for a bomb in 12 days, and would be able to build a bomb within months (though it still hadn't mastered the bomb technology itself, apparently).

Why Iran might be cautious

However, Iran will be more hesitant about intervening than their rhetoric would suggest, due to Israel's unique messaging about their nuclear capability. Unlike most nuclear-armed states, Israel operates under a policy of nuclear ambiguity, which means it has not publicly confirmed nor denied its possession of nuclear weapons. This unusual approach means there is no public line on when and how Israel might employ such weapons, making states like Iran uncertain about where Israel's red line might be.

(It is for this reason that one forecaster highlighted that an Israeli nuclear strike on Iran is plausible. Notably, this forecaster perceived the risk of Russia using a nuclear weapon last winter as orders of magnitude less likely than the rest of the group — at 0.05%, compared to the group's 4%. Here, they are much more concerned.)

A lethal confrontation between the US and Iran is possible but unlikely

While the risk of escalation between Israel and Iran is itself concerning, it also raises the prospect of the United States, Israel's closest global ally, being drawn into direct confrontation with Iran. This scenario is not unheard of — in January 2020, the US conducted a drone strike assassinating top Iranian general Qasem Soleimani near the Baghdad airport. Iran retaliated with missile strikes against US military bases in Iraq.

The specific question our forecasters considered was: "What is the probability of a lethal confrontation between the United States Armed Forces and Iran occurring within the next six months?"

The forecasters collectively gave under a 1 in 10 chance on such an event in the next six months. Here is one forecaster's reasoning:

Senator Lindsey Graham is not in a position to make military decisions, but he did threaten Iran with the bombing of its oil refineries if Hezbollah get involved. This is, however, why President Biden might not want Iran to be attacked by either the US or Israel (oil prices rising in an election year would not be ideal).

President Biden, since the Iraq War, has tended to be fairly opposed to US military interventions (opposing the Afghanistan surge and Libya while supporting the decision not to bomb Syria in 2013).

Whether it is to avoid walking into Iran's "trap", or because it would "represent a complete admission of failure of their foreign policy", many forecasters expected the Biden administration would expend a lot of effort to avoid this outcome.

The conflict could spark major unrest in Europe

Expanding their field of view, forecasters highlighted the possible consequences for Europe in the coming months. As many cities saw significant pro-Palestine rallies in the wake of Hamas' coordinated attacks on Israel, forecasters contemplated the chances of rioting at the same (or greater) scale as the 2011 London riots once Israel actually moves into Gaza.

The London riots were estimated to have caused £200m in property damage — which is roughly $300m in 2023 (after adjusting for inflation). What are the chances a European will see rioting at that level over the next six months?

The group aggregate came to 18% — remarkably high considering the question's threshold number. The marked difference between some governments' support for Israel and the views of the large Muslim populations in their major cities was seen as a key factor.

Zooming out, one forecaster sets out their thinking by looking at the available data for rioting in the US, as well as previous rioting in Europe over conflict in Gaza:

In the United States, which has a moderately smaller population than Europe, riots causing more than $300 million in property damage (in today's dollars) have historically been quite rare. According to a database compiled by Axios, there have only been four since the Second World War, so the base rate is quite low. Interestingly, the ten most destructive riots in the US all occurred from the months of April to August, mostly outside our six month period, and there does appear to be a correlation between temperature and collective violence.

However, we might think that the probability of any riot is higher due to the situation in Gaza, which also pushes up the probability of a very destructive one. There has been rioting in Europe directly linked to the two most serious Israel-Hamas conflicts so far. During the 2008-09 Gaza War, the Oslo Riots occurred. A salon had its windows smashed and five McDonald's restaurants were destroyed, but I very much doubt it reached the threshold of $300 million. Similarly, during the 2014 Gaza War, there were riots in the Paris commune of Sarcelles, which caused some property damage but appears to have been contained to a single day (so it almost certainly didn't reach the threshold).

Notably, this riot occurred after Israel's ground invasion of Gaza, which came almost two weeks after the outbreak of the conflict, so we might expect a ground invasion to trigger a riot.

Since conducting that analysis, Germany and France have banned some pro-Palestinian protests from taking place. This caused forecasters to raise their expectations of large-scale rioting, increasing the aggregate by three percentage points:

I'm increasing my forecast based on Germany and France banning protests. It may work, but is also likely to increase pressure and aim the anger directly against the governments of France and Germany, as opposed to being statements primarily about Gaza. If it happens, I think France is the most likely location.

Another says:

$300m is a high bar, but there is a lot of anger from the Muslim community in France. They were already engaged in serious protests when the French government just came out with a rule saying it is forbidden to protest in support of Palestinians. As the casualties and graphic images emerge from Gaza, blocking protests is likely to serve as a pressure cooker.


The escalating crisis between Israel and Hamas carries global ramifications that extend far beyond the Levant. Our forecasters see non-trivial chances for wider conflict engaging Iran, lethal confrontation between Iranian and US forces, and severe rioting in European cities tied to the tensions.

The overview of the three questions forecasters analysed can be found in this graphic:

For forecasts focused directly on the Israel–Hamas war, read the first part of our analysis, where we looked into the likely number of deaths in Gaza, whether Hamas will retain de facto control of Gaza City, and the degree of Hezbollah's involvement in the coming months.

Illustration by Laurel Molly ©