Verses 1-20
Laws of Warfare
1. Horses and chariots] The army of the Israelites was chiefly composed of infantry: see on Deuteronomy 17:16.
2. The priest] It is implied that the priests accompany the hosts of Israel into battle: see on Numbers 10:9. Hence the Heb. phrase 'to consecrate a war, or warriors,' usually rendered to 'prepare': see Joel 3:9 mg.; Isaiah 13:3.
5-9. From Numbers 1:3 it would appear that all able-bodied men from twenty years of age were liable to military service. But the evils of compulsory service were obviated by the rule laid down in this passage exempting certain classes. There was (1) the man who had built a new house or planted a vineyard, and had as yet got no return for his outlay. The law exempting him for a time was an encouragement to those who by personal outlay increased the material resources of the country. (2) A man who was betrothed or newly married was exempted for a year (cp. Deuteronomy 24:5). (3) The fearful and fainthearted were discharged. Fear is infectious, and the presence of such persons in the host would be a source of weakness and danger. For an instance of the observance of this rule see Judges 7:3. It is implied that a sense of honour will protect this law from being abused.
10. War is to be regarded as the last resort, and only to be employed when negotiations for peace have been tried and failed. In the event of victory, only the fighting men are to be put to death; women and children are to be spared, except in the case of neighbouring idolatrous tribes.
16. Cp. Deuteronomy 7:1-5.
19, 20. Fruit-trees are not to be used for bulwarks and battering rams. The words at the end of Deuteronomy 20:19 should probably be read as in RV, 'for is the tree of the field man, that it should be besieged of thee?' i.e. the tree does no harm and is not to be treated as an enemy. Wanton destruction is not permissible even in war.
All these rules were designed to mitigate as far as possible the evils of war. There is to be no destruction of human life and property beyond what is actually necessary. The conduct of war is to be guided with reason and mercy.