What arose from civilized nations' humanitarian desire to lessen the effects of conflict?

The correct answer is that the law of war arose from civilized nations' humanitarian desire to lessen the effects of conflict. The law of war, also known as international humanitarian law (IHL), encompasses the rules and regulations that seek to limit the effects of armed conflict for humanitarian reasons. It aims to protect individuals who are not or are no longer participating in hostilities, such as civilians and wounded soldiers. The law of war includes various treaties and conventions, notably the Geneva Conventions, which establish standards for humane treatment during military conflicts.

While other options such as international law and humanitarian law are related, they do not specifically capture the intention of regulating conduct during war to minimize suffering. Human rights law, on the other hand, focuses more broadly on the rights of individuals regardless of the situation, not specifically tailored to the context of armed conflict.