Roman philosopher Marcus Tullius Cicero believed that laws were silent amidst the clash of arms. However, the notion that rules were necessary even in times of armed conflict have ancient roots. From the ancient Vedic traditions, Sun Tzu’s ‘The Art of War’, Roman law, the Bible, and the Qur’an, all of these texts include stipulations of what is or is not allowed in war.

These norms have evolved into the contemporary law of armed conflict, which aims to spare those not directly involved in hostilities and limit the effects of violence to the amount necessary for the purpose of war.

They aim to balance the need to uphold humanitarian rules even in times of armed conflict and that of military necessity, which would allow for a party to the conflict to engage in lawful conduct in order for it to win the war. Ultimately, they seek to inject some element of humanity into the awful business that is warfare.

Cardinal Principles

Distinction

The laws of armed conflict are applied when there is a “resort to armed force between States or protracted violence between governmental authorities and organised armed groups or between such groups within a State.“ Therefore they apply to inter-state as well as civil wars.

One of the cardinal principles of the laws of war is that of distinction. This rule states that parties to the conflict shall at all times distinguish between civilians and combatants and between civilian objects and military objectives. Only combatants and military objectives are to be targeted. However, there are certain caveats to the simple statement of this rule. Civilians can be targeted if they directly participate in hostilities for so long as they do so. Moreover, combatants who are injured, surrender, or become prisoners of war cannot be targeted.

The definition of military objective has been subject to debate. The law defines military objectives as “those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage”.

This generally includes armaments factories, missile depots and command centres, however, it can also include bridges if they are used to supply troops to the front line and hills if they offer a vantage point of high ground. Even hospitals can become a legitimate target if they are used to commit acts harmful to the enemy, though the opposing party must give a warning before attacking a hospital.

The US’ position has been that military objectives include ‘war sustaining’ objectives as the military advantage comes from the revenues which allow them to support their military operations. This renders the US’ targeting of oil tankers and cash stockpiles in its war against Isis lawful. This interpretation has been contended and criticised. Legal scholar Marty Lederman, for instance, asks whether this approach would allow a state at war with the US to “target Apple headquarters, or various other tax-generating operations in Silicon Valley.”

Similarly, in its most recent operation in the Gaza Strip, Israel “adopts a highly unusual view” that entire apartment buildings inside which an enemy military facility is found constitute a single military objective that may be targeted. Most other militaries adopt the view that the unit itself is a military objective but the entire building is not. Therefore, there are a number of approaches that states adopt regarding the definition of military objectives which allow for a broader view of what may or may not be targeted during times of armed conflict.

Proportionality

The principle of proportionality provides that the amount of ‘collateral damage’ must be weighed against the military advantage anticipated from an attack. The law itself defines an indiscriminate attack as an “attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated”. A key issue with this principle is the inherent difficulty of weighing civilian life in exchange for military advantage and whether they can in fact be balanced at all.

While many human rights reports in particular simply determine an attack to be disproportionate due to the civilian lives lost, that is not an adequate way to gauge the legality or otherwise of an attack. As military lawyers have stated, “I have approved targets that could have caused 3,000 civilian casualties and I’ve raised questions about targets predicted to risk fewer than 200 civilian lives. The issue is about the importance of the target.” However, the importance of the target itself may be subjectively determined with the importance of the military advantage to be gained being overblown, thereby undermining the calculation made.

In analysing Israel’s attack on the Jabalia refugee camp on October 31, 2023, in which 126 civilians died in the targeting of a Hamas commander, operatives and the tunnel network underneath the camp, Mark Lattimer notes that “the IDF appears to have accepted a level of expected civilian casualties that was not just larger but several times larger than that used by the U.S. and the U.K. in any of the operations during the war against ISIS and other counterterrorism campaigns”. He further questions Israel’s commitment to civilian protection which the principle of proportionality aims to guarantee.

Precaution

The principle of precaution requires that feasible measures be taken to ensure that civilians or civilian objects are not being attacked. If a range of options are available, for instance, in destroying a railway line, it would be preferable to destroy the line in the countryside as opposed to in the city, if this is feasible.

Additionally, the attacking state must take precautions in choosing weapons and tactics to minimise incidental injury and collateral damage and the selecting of military objectives among those giving similar military advantage expected to cause least danger to civilian lives or objects. This principle also obliges parties to endeavour to give warning if feasible to civilians who may be affected by an attack.

However, compliance with the principle of precaution does not mean that any of the other obligations (of distinction and proportionality) are lessened in any way. Israel has in the past issued warnings before air strikes through phone calls, text messages or ‘knocks on the roof. In doing so, Israel argues that it is abiding by international law. It is contended, however, that giving warnings to civilians who in practice have no means to leave may not in fact comply with this cardinal principle.

Conclusion

After the devastation wrought by recent conflicts in Ukraine, Gaza, and Sudan, where the laws of war have been violated and war crimes have been committed, it is a worthwhile endeavour to return to the laws themselves and ask whether they are in fact fit for purpose.

While the norms underlying these rules have ancient roots, it may be that the current indeterminacy with which they are drafted, and the varying approaches to their implementation, undermine the fundamental principles they seek to protect. In order to reduce human suffering amid the clash of arms, it may be that more precise and objective rules are required.

Header image: Displaced Palestinians live in tents near destroyed buildings as they cannot return to their houses, in Gaza City, on October 19, 2025. — Reuters/ File

This article by Ayesha Malik was produced with the support of the International Committee of the Red Cross (ICRC) as part of the Legally Speaking podcast series. The views expressed are the author’s own.