Final answer:
The principle of proportionality does not explicitly prohibit civilian casualties but mandates that any harm to civilians be proportionate to the military advantage gained. The complexity arises when civilians are used as cover by combatants, making it hard to distinguish them on the battlefield. All efforts must be made to avoid or minimize civilian harm.
Step-by-step explanation:
The principle of proportionality in the context of armed conflict does not explicitly prohibit civilian casualties, but it requires that the harm caused to civilians or civilian property must be proportionate to the concrete and direct military advantage anticipated from the attack. The aim is to minimize harm to civilians and ensure that military operations are conducted in a way that balances military necessity against humanitarian considerations. However, it is a complex issue when combatants blend in with civilians or use civilian areas for military operations, which can lead to challenges in distinguishing between combatants and non-combatants, as reflected in historical conflicts.
Civilian casualties that occur despite precautions and adherence to the principle of proportionality may not necessarily violate international humanitarian law, but it is critical that all parties to a conflict take all feasible precautions to avoid and minimize incidental loss of civilian life.