Which principle of armed conflict emphasizes the need to avoid unnecessary suffering?

The principle that emphasizes the need to avoid unnecessary suffering is appropriately identified as unnecessary suffering. This principle focuses on the obligation to ensure that the violence and suffering inflicted during armed conflict are limited to what is necessary to achieve the military objective. It underscores the importance of limiting the effects of warfare on combatants and non-combatants alike, advocating for methods and means of warfare that do not cause excessive injury or suffering beyond what is required for military success.

While the other options—proportionality, distinction, and military necessity—each play a critical role in the conduct of hostilities, they do not specifically address the avoidance of unnecessary suffering in the same manner. Proportionality refers to ensuring that the anticipated military advantage is commensurate with the collateral damage caused. Distinction involves differentiating between combatants and non-combatants to protect civilian lives. Military necessity relates to actions taken that are essential for achieving a legitimate military objective. Each of these principles supports the broader aim of limiting suffering, but the principle of unnecessary suffering specifically targets that goal directly.