I read (recently) for example that:

Philippe Lazzarini, Commissioner General of the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) [...] stressed that such frightening figures cannot be "collateral damage" [...]

Leaving aside whether others agree with him or not on this particular assessment, generally speaking, what methods do experts use to assess such outcomes relative to circumstances? How can one [expert] be rather sure when civilian casualties are excessive in a [modern] conflict?

I'm asking this in all seriousness, I'm not trying to either promote or discredit a particular statement, but I'm intrigued as to its certainty. One can probably find similar ones in other recent conflicts, but I'm not feeling too inclined to turn this Q into a list.

Here's one that doesn't make such a strong claim as to whether that's excessive or not, but dryly notes that

notably in densely populated areas, where civilians accounted for 90 per cent of the casualties when explosive weapons were used, compared to 10 per cent in other areas.

(Apparently that was said by Ramesh Rajasingham, Director of Coordination of the Office for the Coordination of Humanitarian Affairs [OCHA], of the UN.) However that doesn't quite say whether that's "just expected" or perhaps not.

Let's leave aside the obvious cases when death camps are found, otherwise the Q is perhaps too trivial. So, how can experts otherwise assess whether civilian casualties are excessive?

  • What makes you think that the experts to account for circumstances in some sophisticated way? I would assume they just use 'small number = probably ok as collateral, big number=excessive'
    – quarague
    Commented Nov 6, 2023 at 10:39
  • @quarague: well, if that's all there is to it, it's surely a valid answer, as long there's some way to attest to that [way of thinking] more than just by [2nd] guess. Commented Nov 6, 2023 at 10:46
  • And interesting read here although a bit inconclusive. It does point to a book at least, at the end. One issue seems to be that the tools that the DoD uses for such assessments are apparently themselves classified, or at least not public. And they also require expert input. Commented Nov 6, 2023 at 10:58

3 Answers 3


You would have to do a posteriori impartial * investigation on individual casualties or group casualty events.

What was the context? Was this pre-planned targeting (this house hosts a known terrorist)? Reactive targeting (we're taking shots from this house)? What were expected military gains? What types of weapons were used? Were more precise/lower intensity weapons disregarded? Was the presence and amount of civilians known or expected? Did the opposing military even bother to worry about it? Were they told not to? There will be communication and orders logs in military records (their lack would correlate with bad intent, at least in an organized military).

Run enough of these and a pattern starts to emerge. Doing it during the events, unless it's a really clear-cut case in the first place will be hard to do.

There are also some other aggregate indicators however:

Is that military trained to avoid unnecessary civilian casualties? Do they have a post-event investigative procedure? How robust is it (does anyone ever get charged/demoted?) Are screwups frequent? How good is medical assistance for wounded civilians? How do civilian casualties compare to those in similar operations and contexts elsewhere? Are civilians needs otherwise reasonably provided for - food, medicine (cough, the blockade, cough)? Are both sides allowing civilians to get out? Is one side trying to embed itself with civilians instead?

Airstrikes, Civilian Casualties, and the Role of JAGs in the Targeting Process | Lawfare

* Impartiality? That's not a UN refugee advocate's job. Neither is it an IDF spokesperson's.

  • 2
    And even with an impartial investigation, it’s still going to be an open-ended question with a lot of subjectivity. There’s a reason the Rome Statute only imposes punishment when the collateral damage is “clearly excessive” — if reasonable people could disagree on whether it’s excessive, it’s hard to justify individual criminal punishment.
    – cpast
    Commented Nov 7, 2023 at 14:44
  • @cpast That was a bit my thought too as I wrote this. A state/its leadership will get in trouble for war crimes at ICJ. But, if it doesn't, quite, get there, it has a lot of leeway to be quite excessive. Thankfully, the goal posts have moved though: many military campaigns by Western countries in the 50s-60s-70s would never pass muster with their own electorates these days. Commented Nov 7, 2023 at 15:38

There are 3 types of collateral damage: accidental, systemic, and "foreseen proportionality / double effect killing":

(1) genuine accidents or mistakes that were unforeseen and perhaps unforeseeable;

(2) cases of “systemic” collateral damage, where the harm was unintended, yet foreseeable and perhaps preventable — the result of organizational choices and routines, such as rules of engagement and the choice of weapons — yet not necessarily foreseen; and

(3) a category of proportionality / double effect collateral damage where leaders and soldiers know that harm to civilians is likely, but it is judged proportional under the doctrine of double effect because it is not the direct intention to harm civilians.

All of these types of collateral damage killings are legal under current international law.

A war crime or a crime against humanity occurs when these so called "collateral damage" - the death and harm to civilians and civilian infrastructure - is deemed not to be collateral damage. So, the answer to your question is collateral damages are deemed "excessive" when they are viewed through the defined terms of what constitutes a war crime.

All the criticisms directed at Israel, so far, express concern that its specific actions and overall goal in this military action, if not curtailed, can be construed as war crimes:

The United Nations secretary general, António Guterres, said on Monday that 89 employees of the U.N. agency aiding Palestinian refugees, known as UNRWA, had been killed in Gaza in the month of war between Israel and Hamas. That is more “than in any comparable period in the history of our organization,” he told reporters at U.N. headquarters in New York, adding that many of the employees had been killed with members of their family. - U.N. Says Israel-Gaza War Is Deadliest Ever for Its Personnel

Protecting civilians does not mean ordering more than one million people to evacuate to the south, where there is no shelter, no food, no water, no medicine and no fuel – and then continuing to bomb the south itself,” Guterres said ... He said that the “appalling acts” of Hamas “cannot justify the collective punishment of the Palestinian people. Excellencies, even war has rules.” - 2,000 children killed in Gaza, aid group says, as tempers flare at UN amid ceasefire calls

Israel is breaking the rules of modern warfare in Gaza, Norway's prime minister has said. "I believe this is beyond proportionality," Norway's prime minister Jonas Gahr Støre told EUobserver in Oslo ... "The humanitarian consequences for civilians are catastrophic — the number of casualties, the amount of destruction, and especially the enormous burden carried by [Palestinian] children is, as we see it, in breach of what humanitarian norms and standards require," he said. - Israel's Gaza attack 'beyond proportionality', Norway says

The UN secretary general, António Guterres, clearly angered by the impact of the Israeli attack on the Jenin refugee camp, said it had left more than 100 civilians injured, forced thousands to flee, damaged schools and hospitals and disrupted water and electricity networks. “I strongly condemn all acts of violence against civilians, including acts of terror,” Guterres said on Thursday ... “The use of airstrikes is inconsistent with the conduct of law enforcement operations,” he said. Guterres reminded Israel that “as the occupying power, it has a responsibility to ensure that the civilian population is protected against all acts of violence”. - UN chief Guterres condemns Israel’s raid on Jenin refugee camp

(The above is a particularly interesting observation because it suggests that Israel's war itself is in a legal grey area because Israel is an occupying force and is fighting terrorists, which is normally considered a "law enforcement operations" where the military has very limited role).

In Gaza, according to the Ministry of Health, nearly 9,500 people have been killed, including 3,900 children and over 2,400 women. More than 23,000 injured people require immediate treatment within overstretched hospitals. An entire population is besieged and under attack, denied access to the essentials for survival, bombed in their homes, shelters, hospitals and places of worship. This is unacceptable. - Statement by Principals of the Inter-Agency Standing Committee, on the situation in Israel and the Occupied Palestinian Territory, "We need an immediate humanitarian ceasefire"

The director of the New York office of the UN high commissioner for human rights has left his post, protesting that the UN is “failing” in its duty to prevent what he categorizes as genocide of Palestinian civilians in Gaza under Israeli bombardment and citing the US, UK and much of Europe as “wholly complicit in the horrific assault”. - Top UN official in New York steps down citing ‘genocide’ of Palestinian civilians

Queen Rania told CNN claims that a ceasefire will enable more Hamas attacks is “endorsing and justifying” the death of civilians. “I know that some who are against the ceasefire argue that it will help Hamas. However, I feel that in that argument, they are inherently dismissing the death, in fact, even endorsing and justifying the death of thousands of civilians, and that is just morally reprehensible,” she said. - Jordan’s Queen Rania says being pro-Palestinian does not equal being ‘antisemitic’

International Humanitarian Law (IHL) was developed to limit the harm caused to civilians and non-combatants during a conflict / war, and restricts how warfare should be done.

Some of the statements above refer to specific military operations that are part of the war, or to the whole of the war itself. That's because different rules and regulations govern these aspects. For example, when it comes to specific military operations, the "Principal of Proportionality" is used to judge what is "acceptable" collateral damage:

... the principle of proportionality seeks to limit damage caused by military operations by requiring that the effects of the means and methods of warfare used must not be disproportionate to the military advantage sought.

(E.g. - you don't use a nuclear bomb where a conventional bomb will do the job or you don't bomb a whole neighbourhood to kill a few terrorists holed up in one building.)

On the other hand, there's also the goal of the whole war itself that may need to be reviewed under changing circumstances:

Under the law of self-defense, even a legitimate aim must be set aside if it is outweighed by the harmful effects of the force necessary to achieve it. Even if Israel’s right of self-defense is engaged, its current exercise of that right is disproportionate. Israel must either accept an immediate ceasefire, or drastically narrow its war aims and dramatically change its tactics. If Hamas stops firing rockets and releases its hostages, then the war must end there. Israel may not continue to fight until Hamas is destroyed and another three thousand children are dead.

IHL is a vast subject. Please see the references for a more in-depth view that just cannot be covered here in a single post


  1. Accountability for Killing: Moral Responsibility for Collateral Damage in America’s Post-9/11 Wars by Neta C. Crawford.

  2. Enough: Self-Defense and Proportionality in the Israel-Hamas Conflict

  3. Fundamental principles of IHL


This is not so simple. United Airlines Flight 93 had 40 of passengers and crew and only 4 terrorists on board. While the ratio is very not in favor, it was decided that bringing the plane down would be appropriate. This shows that there is no criteria based on just number ratios.

  • 4
    One plane can kill a lot of people on the ground, though.
    – alamar
    Commented Nov 7, 2023 at 7:08
  • @alamar Yes, can, but doesn't have to. One has to weigh the sure death of some versus the potential death of some others. The ratio is probably influences by the expectation/probability and many other things. Commented Nov 7, 2023 at 7:55
  • 2
    @alamar Yep. The balancing test is military benefit vs. civilian harm, not harm to enemy combatants vs. harm to civilians. The shootdown plan wasn’t “shoot it down to kill 4 terrorists,” it was “shoot it down to deprive al-Qaeda of a weapon that we expect is about to cause mass destruction in the US.”
    – cpast
    Commented Nov 7, 2023 at 14:56

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