"When you go out to war against your enemies, and see … an army larger than your own, you shall not be afraid of them” (v1). The Israelites went to war in order to conquer Canaan, and yet they were instructed to always remember that it the real battle was God’s. They didn’t need to fear, despite their inferiority, as long as they were careful to trust and obey God in their all their methods, resisting the temptation to be just like their neighbors (v10-20).
“For the Lord your God is he who goes with you to fight for you” (v4). We can never do battle as the world does; we have different values and a different King.