Under International Humanitarian Law, proportionality requires that any degree of damage (up to and including death) to civlians not be “excessive” in relation to the “military advantage anticipated from a strike against a military target.”
We are going to break that down, so everyone understands what exactly that means.
However, first, you should be aware that it is a misnomer that anytime palestinian civilians die after an Israeli strike, it is automatically evidence of an Israeli war crime. This is completely false - the law does not work that way.
Simply, and unfortunately, the international rules of law recognize that civilians are often killed during war; and, most of the time, those deaths are actually not indicative of a war crime.
Instead, the legal test for “proportionality” requires that each individual strike be looked at with a particular balancing analysis.
First, here is a hard and fast rule: the strike must be intended to target a military objective; it is, therefore, an unlawful war crime to strike with the intent of targeting civilians without any military objective whatsoever.
Now, let’s get a little technical while still keeping it simple.
Under the First Additional Protocol to the Geneva Conventions of 1977 at both Article 51(5)(b) and Article 52(2), we know that when Hamas uses its own population (or Israeli hostage) as human shields - either by using them to shield themselves or to shield their weapons depots - Hamas has, under international law, turned civilians targets into military targets.
That means that when Hamas places weapons caches in and under schools, hospitals, mosques, etc., Hamas has made each of those places legitimate military targets.
So, it has been well-known for many years that Hamas purposefully placed its headquarters underground beneath the al-Shifa Hospital. In doing so, international law holds that the hospital is no longer just a civilian target, it is a legitimate military target.
That does not necessarily give the IDF carte blanche to attack hospitals, schools, mosques, etc.; however, it does mean that an IDF attack on a civilian target that has been made into a military target by Hamas’ use of human shields is not per se illegal under international law.
Instead, such a strike (as is the case with any strike conducted by a military like the IDF), must be analyzed through a balancing test.
One part of this balancing test performed by Israel before each strike is to determine whether the human shields in question are being used voluntarily or involuntarily.
If the human shields are being used voluntarily - meaning the human shields are there protecting Hamas and its weapons of their own volition - then the target remains a completely legitimate military target.
If the human shields are being used involuntarily - meaning Hamas is forcing people to act as human shields to protect themselves and/or their weapons - then the IDF must go back to the balancing test to determine whether the anticipated military advantage of a successful strike would outweigh the reasonably anticipated loss of civilian life.
Importantly, the IDF rules state that if it cannot determine whether a human shield is being used voluntarily or involuntarily, it must presume the civilian is being used against his or her own will and treat the civilians as an involuntary participant.
Assuming that there is a military target & that there may be human shields that are there involuntarily, the next step in the proportionality analysis for each individual strike (remember, proportionality is determined on a strike-by-strike basis, and not as the accumulation of strikes over time) is to try to determine the likely amount of damage to civilian persons and/or property as a result of the strike.
In other words, under international law, Israel must be able to give a sort of “value” to the anticipated impact on civilians (including potential civilian deaths). Simply, a smaller number of anticipated civilian casualties may make the strike proportionate if there is a significant military advantage to be gained by conducting the strike.
However, if Israel determines that the anticipated impact of a strike may cause many civilian casualties, it must make the difficult determination of whether the anticipated military advantage is so significant that it warrants carrying out the strike anyway.
So, if Hamas has a weapons depot underneath a house with two civilians inside, and that house has been used to fire 500 rockets at Israeli civilians, and it is reasonably expected that there are hundreds more rockets under that house, Israel can almost certainly carry out the strike within the confines of international law.
If that same house, however, had 10 families living inside, including many children, it could - and likely would - tip the scales of the proportionality balancing test toward Israel not being permitted to carry out the strike, even though the house has been used to attack Israeli civilians and can be expected to continue to be used to carry out attacks against Israeli civilians.
Now, that balancing test can always change. If that same house is being used to fire long-range, precision-guided missiles at Israel’s major population centers in places like Tel Aviv (effectively putting millions of Israeli civilians in danger), the balancing test may tip back in favor of Israel being legally permitted to carry out the strike.
This all suggests the third and final step in the proportionality balancing test: the IDF must determine and place a “value” on the anticipated military advantage that would be gained if it were to carry out a particular strike.
An attack on Hamas leadership and/or its weapons manufacturers would be considered a high value target. An attack on a single Hamas member who has no special skill, would be a much lower value military target.
Similarly, an attack on a small cache of mortars would have less military value that an attack on a large cache of advanced rockets that can reach large Israeli civilian population centers.
Once the IDF determines the anticipated “value” of the likely effect on civilian persons and property and the anticipated “value” of the likely military advantage to be gained if the strike is carried out, the balancing test can be performed, and a certain amount of judgment must go into the determination of whether that strike would or would not be “proportionate.”
Importantly, this decision is so vital that the IDF does not simply permit a single solder on the ground with his or her hand on the proverbial (or actual) “trigger” to make that determination.
In fact, the decision of whether a strike is proportionate is not even left up to IDF officers. It’s not even left up to IDF Generals.
Instead, before any IDF strike can take place, IDF Guidelines provide that the proportionality balancing test must be presented to and analyzed by IDF military lawyers who then determine whether the strike is legally permissible as “proportionate” under international law and the rules of war.
And these IDF military lawyers are not mere patsies or people who simply “rubber stamp” what the IDF requests.
In fact, the IDF’s military lawyers work entirely independently of the IDF. They are outside of the chain of command and do not answer to anyone in the IDF, including a General (for example).
Plus, every IDF military lawyer knows he or she may very well be held to account if he or she makes a wrong decision based on the evidence available at the time.
Furthermore, sometimes the decisions to be made while balancing the likely military advantage against the likely civilian casualties can be so difficult that the legality of the strike is first brought to the Israeli Supreme Court for instant review.
Another important concept: the comparison of civilian body counts of Israeli versus Palestinians (to the extent those numbers can be trusted since they come directly from Hamas-only) is not relevant to a proportionality analysis. Each strike must be viewed individually to determine proportionality. It is not a test of the cumulative nature of the strikes.
Also, by simply comparing body counts, it does not factor in how many people killed were actually Hamas Terrorists, how many were Hamas collaborators there voluntarily, and it does not consider what military advantage was gained by Israel carrying out any individual strike.
As Israel is now in the process of seeking to secure the military advantage of preventing Hamas from having the capacity to carry out repeated attacks of the kind and nature seen on October 7th, Israel is permitted to act proportionately insofar as necessary to achieve that military objective (the elimination of Hamas and/or its ability to make war).