Israel’s war on Hamas is set to eclipse all previous Arab-Israeli conflicts

Israel-Hamas forecasting part 1: of all the wars in the last 75 years of Arab-Israeli conflict, this one is probably going to be the deadliest.

Israel’s war on Hamas is set to eclipse all previous Arab-Israeli conflicts
Illustration by Laurel Molly, © All Rights Reserved

Overview of the next six months:

  • 61% chance there will be over 25,000 deaths in Gaza
  • 20% chance Hamas retains de facto control of Gaza City
  • 56% chance Israel–Hezbollah fatalities will exceed 500.

It has been less than one week since Hamas staged its deadliest-ever attack on Israel, and Israel appears poised to launch a full-scale ground invasion of Gaza in an effort to wipe out the group.

On October 7th, Hamas militants based in Gaza invaded Israel, killing over 900 Israelis in towns near the Gaza border and taking hostage both soldiers and civilians before retreating back into the coastal Palestinian enclave. The assault, dubbed "Operation Al-Aqsa Flood" by Hamas, shocked Israelis and much of international community with its scope and brutality. Israel responded with overwhelming air and artillery strikes on Gaza, but has yet to send in ground forces.

It remains uncertain exactly how events will transpire over the coming weeks and months. To gain insight into how the conflict may proceed, we selected six forecasting questions on important factors that could characterize the conflict's trajectory over the next six months. The top-performing forecasters that the Swift Centre is comprised of drew on historical precedents from past Arab-Israeli wars, other urban battles, as well as an assessment of factors unique to the current environment.

It is highly likely that Hamas will lose control of Gaza City in the coming months

The Israeli government has exhibited an unwavering stance against Hamas. Their intent appears to be not just to retaliate but to decisively eliminate the threat that Hamas poses. This approach, supported by a mobilization of around 300,000 troops, significantly outweighs that of the force against ISIS in the Battle of Mosul, which had a strength of approximately 108,500-114,000 troops.

Considering Israel's manpower and determination, it is hard to envision Hamas retaining control of Gaza City. Still, as prolonged street-to-street fighting favors defenders, forecasters gave a 20% chance to Hamas retaining de facto control of Gaza City in six months' time. Israel would likely face similar challenges as Iraq and the US-led coaltion had against ISIS in Mosul in 2016–17. One forecaster's viewed the conditions as challenging for the Israel Defense Forces:

It is very unclear to me how long it will take the IDF to clear Gaza of Hamas’s presence, given the IDF’s relatively mediocre performance in Lebanon in 2006 and again in Gaza in 2014. Urban combat has a long history of being extremely tough for the attacker against a well-prepared, dug-in foe, even when the attacker has a numerical and technological advantage.

However, most forecasters assessed the chances of Israel achieving regime change in Gaza City within six months as highly likely. From the outset, everything said by those in charge in Israel leads one to believe that the chance of Hamas remaining in power for long is slim. As one forecaster explained, "Initial reactions within Israel point strongly toward a 'gloves off' response, and early comments from major allies appear — for the moment — to give Israel carte blanche."

Public resolve in Israel to defeat Hamas appears high after the trauma of recent attacks. Israel seems willing to bear substantial military and civilian costs to decisively end the threat posed by Hamas in Gaza City. As one analyst noted, "It was never a question of capability of taking out Hamas in 2009 or 2014 but rather political will. Due to the situation today this is not a factor."

The challenges that forecasters cited for not providing probabilities closer to 0% were:

  • Clearing tunnels street-by-street will likely take months, if that is how Israel choose to proceed.
  • Tanks will be vulnerable to ambushes.
  • Hamas's technological sophistication (including the effective use of drones) has improved, probably with Iran's help.
    • (For more on the challenges of a ground invasion of Gaza, forecasters found this article useful.)
  • Wider conflict with Hezbollah could divert resources from the push into Gaza City.
  • Fully re-occupying Gaza City may not align with Israel's strategic objectives.

Indeed, on that final points, reports say there is little appetite for reoccupation of Gaza. However, several forecasters do not believe it is out of the question. Israel occupied Gaza from 1967-1993, and partly until 2005. Temporarily re-occupying Gaza City to oust Hamas, while not politically ideal, is not an implausible scenario given this historical precedent.

61% chance the death toll in Gaza is >25,000

In an effort to gauge the potential loss of life, forecasters were asked whether they expect the death toll in Gaza to exceed 25,000 — a figure that surpasses the death toll of any previous Arab-Israeli war. This question is concerned with both combatant and civilian losses, but exclusively within Gaza (not the surrounding regions).

The forecasters assessed a 61% chance that the death toll in Gaza could exceed 25,000 over the next six months. While historical precedent might suggest this grim projection is unlikely, this situation appears fundamentally different to the past. The 2014 Gaza War lasted 7 weeks and resulted in around 2,400 deaths. But Israel's goals then were limited to stopping rocket attacks, not removing Hamas from power. The fact that so many consider this situation to be "Israel's 9/11" suggests Israel will have an elevated willingness to absorb casualties to achieve decisive results.

Comparable sieges such as Aleppo, Sarajevo and Mariupol provide mixed lessons. Their timescales range from several months to over four years, and their death tolls range from 14,000 to (possibly) 45,000. Forecasters believe Hamas is likely to fall faster than these examples, but its resistance could still prolong the conflict. The Battle of Mosul remains the closest example to this current conflict; its death toll is highly uncertain (as this one's will be), with estimates ranging from 15,000 to 32,500 over 9 months.

Civilian death toll

High civilian deaths are very likely given Gaza's dense population and Israel's willingness to use overwhelming firepower. Additionally, with Gaza under blockade and nowhere to escape to, civilian suffering is inevitable. The civilian death ratio in 2014 was around 70% according to Palestinian sources. Israel's current "gloves off" approach, combined with the 20% growth in Gaza's population since 2014, could produce similar or greater casualty ratios.

Exacerbating the situation is the misinformation persuading civilians not to listen to warnings about imminent attacks. As a humanitarian measure, Israel issues advance warnings to Gaza residents advising them to evacuate specific buildings that have been identified as targets for airstrikes. However, Gaza news outlets actively urge residents to ignore them. On Wednesday, Gaza Now posted on X to say "Since the beginning of the war... the Israeli occupation is trying to control Gaza by sending different codes and emails as if they are from official bodies. Once they are clicked on, our accounts are fully hacked. Thanks to God, our team is awake and is thwarting the repeated attempts of the occupation. We continue with you." (Link)

Another tweet later that day stated: "The occupation is trying to spread false news by calling the families and demanding them to evacuate immediately. Please do not deal with these warnings at all. The occupation aims from these calls to create confusion and spread fear among our people in the streets of Gaza." (Link)

This morning, Israel gave the unprecedented directive for 1.1 million civilians living in Gaza City to evacuate to the south. While the Israeli military acknowledges the logistical challenge in relocating such a large number within a day, they attribute non-compliance to Hamas instructing residents to disregard the evacuation call.

While such an evacuation could result in fewer fatalities, the news caused forecasters to adjust their fatality projections upwards, as it signifies the intended strength of Israel's coming military response. Additionally, a press statement says that the UN "consider it 'impossible' for such a movement to take place without devastating humanitarian consequences and appeals for the order to be rescinded".

Combatant losses

Forecasters expect combatant losses to be high, too. Here is one forecaster's reasoning for expecting a death toll of over 25,000 in Gaza:

Base rates of number of casualties are useful for perspective, but this attack is unprecedented, with the highest number of Jews being killed in a single day since the Holocaust. This is very, very different from the previous operations in Gaza or even Lebanon. I think that Israel [..] is very, very serious about eliminating Hamas.

In 2021, a senior Israeli commander estimated Hamas' strength in Gaza at around 30,000 fighters (though one forecaster points out that "the definition of 'fighters' is probably a loose one, ranging from committed jihadists willing to die all the way down to untrained militiamen with a rifle").

Historically, casualty ratios between the IDF and Hamas have been greatly skewed. The 2014 Gaza War saw 40 Palestinian militants die for every 1 Israeli soldier, so forecasters anticipate that losses among IDF will not make up a large proportion of the total death toll. They do expect the IDF will suffer a significantly higher number of losses than they have in previous conflicts, with one forecaster arguing the following:

Israeli military casualties in the Gaza Strip could be quite high, as they could be vulnerable to ambushes and will be operating in an area where the civilian population is hostile to the Israeli military. Hamas's technological sophistication (including the effective use of drones) has also improved, probably with Iran's help.

Pressures to de-escalate

One forecaster who expects the death toll to remain under 25,000 anticipates that pressure from the U.S. could prevent the death toll from climbing so high. Another forecaster sees Israel's potential willingness to relax the Gaza blockade as an indication that they may consider de-escalation. Most forecasters do not expect the brakes to be applied soon, however, with forecasters noting how seemingly all Israeli politicians, not just the right wing, are intent on eliminating Hamas.

Hezbollah joining the conflict is a realistic possibility

A key factor causing uncertainty in forecasters' expectations about the timescale (and military dominance of the IDF) during this conflict is the possibility of sustained fighting breaking out between them and Hezbollah in Israel's north.

The most fatalities between these two groups, as recorded by Armed Conflict Location & Event Data Project (ACLED) since 2016, stands at 11 over any six-month period. Hezbollah has been significantly more active in Syria, and has lost 1,736 fighters there since the Syrian civil war broke out in 2011, according to the Syrian Observatory for Human Rights.

This recent involvement in Syria may, however, push Hezbollah into more direct conflict with Israel. Daniel Byman in Foreign Policy explains that although Hezbollah was primarily founded to combat Israel, its intervention in Syria has eroded its reputation amongst Arabs, since it aided the Alawite-led Syrian regime against a predominantly Sunni opposition. As a result, Hezbollah may feel compelled, perhaps by Iran, to reaffirm its anti-Israel stance.

We forecasted on the question "Will there be 500 fatalities from Israel–Hezbollah confrontations over the next six months?" By this, we specifically mean fatalities during incidents involving Hezbollah and either the IDF or Israeli civilians, as recorded by ACLED.

The group were highly uncertain, putting 56% on Hezbollah–Israel fatalities reaching this level over the next six months, with a large spread of views among them.

Initially, our threshold of 500 fatalities in a six-month span was seen as a proxy for Hezbollah being a third belligerent in the war. Yet, with 8 fighters from both sides dying in just one day, the bar does not appear to be so high. Regardless, any number approaching or exceeding 500 would be a significant uptick in violence between Israel and Hezbollah, consuming resources Israel would otherwise dedicate to Gaza.

Reasons for the group's uncertainty

Our forecasters cogently explain the reasons for uncertainty here:

Hezbollah hasn't officially entered the conflict yet, but there have been some skirmishes between Hezbollah fighters and Israel. There are conflicting reports on what, if anything, would lead to Hezbollah's entrance. The Lebanese Foreign Minister claims that Hezbollah would only enter if Israel attacks Lebanon (though Israel has already struck Southern Lebanon).

Some, including the Iranian Foreign Minister and Hezbollah’s Deputy Leader, claim that Hezbollah would attack if Israel launches a ground assault on Gaza. Meanwhile, the US and Hezbollah have been trading threats, clearly trying to deter each other from getting involved. Hezbollah probably doesn't want to get involved in a direct confrontation with the US. Still, it may be pushed further by Iran. Even if they do get involved, there's still a non-negligible probability that there wouldn't be 500 fatalities — some estimates suggest that there were fewer than 500 military fatalities during the 2006 Lebanon War; others suggest there were more.

Overall, I thought the US's strong warnings for others not to get involved (exemplified by Biden's repeated statements to that effect) were more likely than not a sufficient deterrent, but with high uncertainty, and the statements from Iran’s Foreign Minister and Hezbollah suggest that they haven’t been deterred.

Another forecaster emphasises Hezbollah's readiness to get involved:

Hezbollah has stayed out of the war so far, but I'm very uncertain what their overall plan is. It could be that they are waiting to see Israel invest significant resources in Gaza before attacking, and using the destruction that will be caused as a pretext.

I think this would be an unwise move for Hezbollah, as I'm confident they'd lose. Nevertheless, they may have as many as 150k missiles, so they have clearly been preparing for a situation like this.

The forecaster who most strongly thinks this is unlikely over the next six months gave the following reasoning:

I've been surprised at how quiet things have been, if there were going to be a northern front. There was a tactical engagement resulting in the death of 3 Hezbollah fighters, along with a rocket barrage and Hezbollah statement threatening Israel, but otherwise it has been fairly quiet. Although Hezbollah and Hamas share a common enemy with Israel (and both are sponsored and supported by Iran), they have different geographical and political focuses, as well as Hezbollah being Shia while Hamas is Sunni. There is also the Iranian “crossroads of fire” concept, discussed by the Washington Post here, with the idea being to launch an attack on Israel every few months or years as a long-term campaign to sap its morale and viability. And so in the recent past, it's been more of a one-two punch with, for example, the July 2006 Israel-Lebanon War coming a year after the Second Intifada.

I would also note the fact that Iran has spent decades now expanding its influence in Syria and Lebanon, and to lose both its Gaza proxy and its Lebanon/Syria proxy would be an enormous destruction of its geopolitical influence. The US is moving the USS Gerald R. Ford Carrier Strike Group to the eastern Mediterranean, adding further deterrence.

Reasons given for Hezbollah's involvement in the conflict

On the other hand, there were many reasons given by others for why Hezbollah would get involved:

During the last ground invasion of Gaza by the IDF in 2014, Hamas urged Hezbollah to join the fight and open the second front, but this didn't happen, likely because Hezbollah was then engaged in intense fighting in Syria. This time, Hezbollah does not appear to be that much preoccupied elsewhere.
Israel and Hezbollah have been killing each other daily, but with some restraint. Once the ground war in Gaza starts, it will become increasingly difficult for Hezbollah to stay out of the heavy fighting. Their support comes from Iran and they have an extensive tunnel system of ~150,000 missiles and rockets. An unknown is whether the US will intervene with air power.
1) Israel would certainly be challenged to fight on two fronts at once, so Hezbollah might roll the dice even at risk of its destruction, if it sees a narrow window of opportunity.
2) ISW reports that Hezbollah is moving fighters to southwest Syria [closer to Israel].
3) Israeli forces are reported to be massed in the north. Of course, this also means Israeli assets are diverted and distracted without any fighting needing to happen.
4) Recent warnings from Israel's Defense Minister Yoav Gallant.
Hamas's action only really make any sense as part of a coordinated plan involving Hezbollah to force the IDF to fight on two fronts, so at the least I expect some action from the IDF to deter Hezbollah from entering the conflict, and I also expect at the very least plenty of probing actions from Hezbollah. 

Making the most of mobilisation?

An alternative path to this question resolving positively was provided by another forecaster on a forecaster call. “If this goes reasonably well for Israel (i.e. they achieve their main objectives in a few weeks) you can see how they might think 'while we're fully mobilised - let's fully destroy Hezbollah now.' It's a possibility, especially if we're talking about the next six months," the forecaster noted. “Some might think about occupying South Lebanon again,” they argued. Expanding on their thinking after the call:

For all the differences between the two cases, the Israeli withdrawals from South Lebanon in 2000 and from Gaza in 2005 followed a similar logic: to reduce the burden of actively occupying areas that Israel does not deem vital (as opposed to the Golan or the Jordan Valley) and to take a mobilising cause for its enemies away.

The idea was that it would be possible to mostly seal off the borders, establish deterrence and protect oneself without exposing Israeli troops to permanent (potential) enemy contact.

It's hard to argue that these goals have been reached. In both cases, conflict is far greater than what we had seen in previous years (Lebanon 2006, Gaza 2008).

They point out that Israel's image in the global public eye has not improved much, but they are seeing more support now. "Now, the costs of occupying these areas and assuming full responsibility for many aspects of life there seems much more acceptable."


Swift forecasters selected six key questions as a basis for quantifying their beliefs about the current conflict between Israel and Hamas. In this report, we have covered the first three, which you can see summarised in this graphic:

The forecasters at Swift, who often outperform others by accurately placing probabilities on events, become adept by familiarizing themselves with base rates — the underlying probabilities for various outcomes based on historical data. A successful forecasting strategy often involves adhering closely to these base rates, unless there is good reason to expect deviations. In this instance, forecasters' predictions diverge significantly from the base rates: they assign an 80% chance to Hamas being ousted from Gaza City (after ruling it for 16 years), and a 56% chance of witnessing a death toll unprecedented in the past 75 years of the Arab-Israeli conflict.

The remaining three questions are concerned with how the conflict may escalate internationally, and will be covered in our second report on the topic.

Illustration by Laurel Molly ©