War is brutal, but that brutality is often mitigated by culturally accepted rules. In later Mesoamerica, the Aztec flower wars (shed blood was often depicted as a flower) were ritualized battles by appointment, designed for individual warriors to achieve personal glory through battle and capturing prisoners to sacrifice to the gods. Whether we agree with the cultural rules, they do in fact impose some limitations on what is “acceptable.”
Mormon’s lament that his commands are not followed introduces a catalogue of offenses (v. 19) which are counter to the accepted rules of warfare. Mormon sees that his army has become “alike brutal, sparing neither old nor young.” The Nephite army had faced a situation where the rules of warfare had been changed unilaterally, imposed by Lamanites who were influenced by the Gadiantons. The way that they had previously fought might be seen as a collection of “gentlemen’s rules” of honorable warfare. Those “gentleman’s rules” had been horribly violated in this new destructive style of warfare. No doubt, for a while the Nephites maintained their honor by following the old rules even though the enemy was violating them; but clearly, at this point they have begun to imitate their enemies. Thus did they become “alike brutal.” Mormon now uses the Nephite “women and children” as moral witnesses against the Nephite men. The “women and children” maintain the “proper” understandings while the fighting men have become brutal, delighting in “everything save that which is good.”