What importance does a war crime have?

Deliberate assaults on the people and property of neutral governments, like the Japanese attack on Pearl Harbor, were also considered war crimes. The attack on Pearl Harbor was deemed to go beyond justification of military necessity and therefore constituted a war and crime by the Tokyo Trials since it took place while the United States and Japan were at peace and without a reasonable cause for self-defense. Due to the fact that international tribunals like the Nuremberg Trials and Tokyo Trials have convened in this field, war crimes are serious under international humanitarian law