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Conduct of Hostilities: General Principles

The conduct of hostilities is a specific aspect of international humanitarian law (IHL) which regulates the means and methods of warfare. This area if often referred to as traditional Hague law. It is an area of IHL where protection is often seen to be relatively weak, with more of a focus on restrictions as opposed to prohibitions.

Regulating hostilities

Naturally, it is when warring parties engage in hostilities and in military battles, that armed conflict is usually at its most violent and brutal. The protections provided by IHL in this area are often seen to be rather weak, with a focu on restrictions instead of absolute prohibitions.

This is due in part to the reluctance of states to be restricted too much when they launch and engage in military operations. Many rules are subjective in nature and are not results based, instead based on a good faith perception of the facts at the time of the attack.

Core principles

For an attack to be lawful it must respect all three core principles that regulate the means and methods of warfare:

There must be a lawful target of attack;

The expected harm to civilians must not be disproportionate to the military advantage to be gained;

All feasible precautions must be taken to limit the harm caused. If any information comes to light changing the assessment under the first two principles and that might suggest unlawfulness, then the strike must be suspended.

The principle of distinction: civilians and military targets

The principle of distinction prohibits all direct attacks against civilians and civilian objects, as well as prohibiting all means and methods that cannot make a distinction between civilian and military targets.

If the principle of distinction is violated, there is no need to discuss  the principle of proportionality.

Read more about the principle of distinction and who and what can or cannot be targeted during hostilities

The principle of proportionality

The principle of proportionality (Article 51(5) (b) API) states that a military target cannot be attacked if the risk of civilians, or civilian property, being harmed as a result of the attack is larger than the expected military advantage.

If the target attacked is a civilian object, no discussion is needed on proportionality, as any intentional direct attack against a civilian object is a violation of IHL and very probably a war crime. 

Read more about the principle of proportionality.

Precautionary measures

In addition to the rules on targeting and proportionality, conflicting parties are obliged to respect the principle of precautions in attack and in defense. This principle includes requiring warring parties to undertaken feasible warning, as well as chose means and methods of attack that will cause the least amount of civilian harm. In the case of military defense, parties must refrain from situation military objects in densely populated areas.

When it comes to hospitals that may have been used for military purposes, an effective warning must be given.