Moses provides the Israelites with instructions regarding their behavior in battle against the Canaanites, reassuring them that the Suzerain (Ruler) God Yahweh is the one who fights for them as He has done in the past. Therefore the people are to be courageous and fight, unlike their fathers, who refused to fight out of fear. This chapter consists of three directions for warfare: preparing and encouraging the Israelite army for battle (vv. 1-9), instructions for battle against adversaries far and near (vv. 10-18), and protection of trees when cities are besieged (vv. 19-20).
Deuteronomy 20 can be outlined as follows:
–The Law Concerning the Preparation for War (Deut. 20:1 – 9)
–The Law Concerning the Conduct of War (Deut. 20:10 – 18)
–The Law Concerning Fruit Trees (Deut. 20:19 – 20)

Deuteronomy 20:1-9

Moses commanded the Israelites not to fear their adversaries in the event of war because Yahweh, the great warrior, is the one who fights for them.

Deuteronomy 20:10-18

Moses prescribed regulations concerning how the Israelites are to conduct themselves in war against adversaries that are either far or near.

Deuteronomy 20:19-20

Moses asked the Israelites to protect the trees when they besiege a city. Non-fruit bearing trees could be cut down and used in building siegeworks, but fruit-bearing trees were to be left intact in order to produce food for the Israelite army.