Deuteronomy
Chapter 20
Law on War
When you go to war against your enemies and see horses, chariots, and an army more numerous than yours, then have no fear because the Lord, your God, who brought you out of Egypt, is with you.
When the hour of battle draws near, the priest shall advance to the head of the army and speak to the people saying,
“Listen, Israel, today you are to enter into battle against your enemies. Do not let your heart be discouraged, or afraid, or troubled, and do not tremble before them,
for the Lord, your God, is with you, to fight in your favor against your enemies and save you.”
So the secretaries shall say to the people: “Is there anyone of you who has just built a new house and has not dedicated it? Let him go home, lest he die in battle and another dedicate it.
Is there anyone among you who has planted a new vineyard and has not yet enjoyed its fruits? Let him go home, lest he die in the war and another enjoy its fruit.
Is anyone who has promised to marry and has not yet been married? Let him go back to his home at once, lest he die in combat and another take the woman as his wife.”
They shall also say: “Is there anyone afraid or weakhearted? Let him go home immediately, lest his fear discourage others.”
When they have finished speaking, commanders shall be put at the head of the people.
When they have finished speaking, commanders shall be put at the head of the people.
When you draw near to a city to lay siege to it, you shall first offer it peace.
If it accepts your proposal and opens the gates to you, all the people found in it shall become your slaves and serve you.
If they do not accept the peace that you offer them and declare war against you; you shall lay siege to the city.
When the Lord, your God, gives it into your hands, you shall kill by the sword all the men,
but the women and children, the livestock and all the other things which you find there shall be your booty. You shall eat from the plunder of your enemies, which the Lord has given over to you.
This you shall do to all the cities which are very far from you and which are not in the country which you will possess.
But in the cities, which the Lord gives you as an inheritance, you shall not leave anything that lives.
You must destroy them all according to the law of anathema—the Hittites, Amorites, Canaanites, Perizzites, Hivites, and Jebusites—as the Lord, your God, has commanded you,
that they may not teach you all those evil things which they have done to honor their gods, for by imitating them you shall sin against the Lord, your God.
If, when attacking a city, you have to lay siege to it for a long time before capturing it, you shall not destroy the fruit trees around it nor cut them with your axe so that you may eat their fruit. Do not cut them, then. Are the trees of the field men that they should also be stricken?
If trees in the field are not fruit-bearing but are for other uses, cut them down and make ladders and instruments out of them with which you may seize the city that offers you resistance.

Commentaries
Law on War.
The first part of this chapter (1-9) explains the steps to take before going to war against any enemy; it is understood that combat is part of a religious duty overseen by the priest, who emphasizes that the war Israel fights is of the Lord, so there is no need to be afraid (1-4). After the religious ceremony, there should be a civilian address stressing that other matters are more important than the war itself: building a new house (5), harvesting crops (6), getting married (7), and if none of these prevent someone from joining the army, simple fear or cowardice can be used as reasons to stay home (8), which could be seen as a legitimate reason for conscientious objection.
The second part (10-20) covers the “methodology” of war. Always prioritize dialogue and peace negotiations (12-18) before turning to other tactics. The methods used against enemies may seem shocking and even barbaric, but we must consider the context in which these texts were written.
Verses 19f serve as a strong example of care for the environment, sharply contrasting with the deadly and anti-ecological results of modern warmongering, which endanger everyone’s lives.