God As Commander
Moses now discusses the principles governing warfare. These principles show that, despite the use of physical armaments, Israel was still to look to God for victory (Deuteronomy 20:1-9). One of the threats that Israel would face in war mentioned in verse 1 is "horses and chariots." Armies equipped in this manner were particularly intimidating to foot soldiers. The commandment was given in Deuteronomy 17:16 that Israel's kings not "multiply horses." And there is no evidence that Israel utilized horses for war before Solomon's time (1 Kings 4:26; 1 Kings 10:26). If this is the case, it is particularly fitting that Moses assured Israel they need not fear even when armies came against them with chariots.
With Almighty God as commander, there was no room for fear in the ranks—and those who were fearful were to be excused (verse 8). Others excused from warfare—at least on a temporary basis—included a person who had just built a new house, one who had planted a new vineyard, and one who was betrothed to a woman to marry her (verses 5-7). Deuteronomy 24:5 adds the further exception of a man who had just gotten married—he was permitted to stay with his wife for one year without having to go out to war. One of the reasons for these excuses from participation in battle seems to be that persons in such conditions would likely be thinking about what they were leaving behind rather than concentrating on the battle. No doubt, God's mercy and compassion are also shown in these regulations. Furthermore, in these "excused absences," God was showing that it is not necessary to rely on numbers. With God fighting for His people (verse 4), very few people could easily overcome a force of many times their number (see Leviticus 26:8), as often happened during the Israelites' history when they were obedient to God.
Before the Israelites attacked a city "very far" from them (Deuteronomy 20:15), they had to offer peace to it (verses 10-11). It is interesting that the offer was of peace—not enslavement. Such cities were to pay tribute, essentially a tax, and "serve" Israel—not in slavery but to remain in peace and harmony with Israel, thus promoting the safety, security and well-being of God's people. Moreover, in agreeing to keep Israel's laws and way of life, such cities would in fact enter into a much better way of life than they had ever known. If a city refused the offer and chose war instead, Israel was to "strike every male in it with the edge of the sword" (verses 12-13), while leaving the women and children alive (verse 14). In regard to the cities that were located within the Promised Land, however, Israel was to "let nothing that breathes remain alive" (verse 16), so that the evil inhabitants could not influence Israel with "their abominations...and you sin against the Lord your God" (verse 18).
Finally, God told Israel not to cut down fruit trees in a siege against a city. They were only allowed to destroy those trees that were not "trees for food" (verses 19-20). This would especially make sense in a longer siege where food supplies could become an issue.