If it does not accept terms of peace but makes war with you, then you are to lay siege to it.

Then the Lord said to me, “Do not harass Moab and provoke them to war, for I will not give you any of their land as your territory. This is because I have given Ar to the descendants of Lot as their possession.

Get up, make your way across Wadi Arnon. Look! I have already delivered over to you Sihon the Amorite, king of Heshbon, and his land. Go ahead! Take it! Engage him in war!

However, you may chop down any tree you know is not suitable for food, and you may use it to build siege works against the city that is making war with you until that city falls.