Read up on the Geneva Conventions. War is brutal, yes, but at the end it's a conflict between state powers & while violence is necessary to force the issue, a line must be drawn. See the use of economic sanctions as a method to compel without direct violence. There's enough power between parties which agree to the Geneva Conventions so that if one party is not agreeing to those terms, additional resources can be tapped from allies

Unfortunately it feels the US is powerful enough that the international community isn't stepping in with sanctions against the US