The Old Testament is full of God inspired slaughter. In some cases, God does the killing himself. But in many cases, he orders his followers to kill for him. In fact, some of his most wicked anger falls on the men who show mercy on a king after God has commanded genocide.
But this begs the question, why does God need us puny humans to kill his enemies? After all, with swords swinging, we are at very real risk of injury from his enemies. But from God’s vantage point, he could simply declare, “Death to the Midianites!” and poof, they would be gone. For that matter, maybe he could have avoided creating them in the first place.
The next thing that is of concern is the question of proving that God actually told the commander (in most of these cases, Moses) to perform the genocide. How would the Israelites have known whether these enemies were enemies of God or of Moses? I know that now we are very suspicious when someone claims that God told them to kill someone. Apparently, back then, people were more trusting.
When this topic comes up and a Christian apologist is explaining God’s justice in genocide, I like to quip, “Good thing God isn’t commanding these genocides now or the followers would face war crimes charges.” It’s good that God commanded these killings when communication was limited.