In Deuteronomy 20, Moses prepares Israel for war—calling them not to fear because the Lord goes with them to fight. In this passage, we learn that our God is holy and just, that he uses war to judge the wicked and defend the righteous, and that biblical principles undergird what later theologians called just war theory. Above all, we are reminded that our primary battle is spiritual: not against flesh and blood but for the conversion of sinners through the gospel, as Christ is with us and fights for us. So we must not shrink back, knowing our cause is just and our God is great.