The priest will address the people and offer the following exemptions from military service: (1) building a new house, but not having dedicated it; (2) being engaged, but not married; (3) being afraid to fight.
A little different than the modern draft exemptions, wouldn't you say?
Did you notice that in Exodus, we only get descriptions like "They went to war"? Deuteronomy has a different agenda than just telling a story. It's taking the older stories and adding to them many layers of law.
Speaking of law, when you approach a city, offer a peace treaty. If they don't accept it… attack.
Kill all of the males on the opposing side. In the towns that are farther from you, take women, children, livestock, and their stuff. The Bible calls this booty.
How do we reconcile this with the Ten Commandments?
If it takes a long time to conquer a city, don't destroy the fruit trees. You can, however, use the trees that don't produce fruit to help you siege the city. Battering rams, anyone?