This is an article I received from the Torah.org Halacha mailing list I am on. I think some JTF members may find this interesting:
http://www.torah.org/learning/halacha-overview/chapter83.html83. Kings and their Wars - Melachim u-MilchamoseihemSeven commandments apply to non-Jews: idolatry, blasphemy, murder, fornication, robbery, eating from a living animal (as Noah was commanded, "But flesh with its life, its blood, you shall not eat"[1]), and justice.[a]
We are commanded to appoint a king over Israel, as it says "You shall put over yourself a king".[2] He must not be a proselyte, as it says "[From among your brothers you shall put a king over yourself;] you may not put over yourself a strange man who is not your brother".[2] He must conduct himself humbly; in particular he is forbidden to take many wives or have many horses or have excessive wealth, and he is commanded to carry a copy of the Torah with him everywhere, as it says "But he shall not have many horses... and he shall not have many wives and he shall not have very much gold and silver... and he shall write himself a copy of this Torah... and it shall be with him and he shall read in it all the days of his life... so that his heart shall not be high above his brothers...".[3] He has the power to punish rebels, to levy taxes, to conscript soldiers, and to take (and pay for) whatever he needs.[ b]
One should live in the land of Israel if possible, and it is forbidden to leave the land except when necessary. It is forbidden to settle in the land of Egypt, as it says "[As you have seen Egypt today] you shall never again see them"[4]; and it says "[He shall not return the nation to Egypt... and Ha-Shem has said to you] `you shall never again return on that road'"[5]; and it says "[Ha-Shem shall return you to Egypt in ships on the road of which I said to you] `you shall never see it again'".[6,c]
We are commanded to destroy the seven nations of Canaan and it is forbidden to let any Canaanite live, as it says "[But from the cities of these nations...] you shall not let any soul live; for you shall destroy them... [in order that they do not teach you to imitate all their abominations]".[7] It is forbidden to forget the evil deeds of Amalek; we are commanded to remember them and to destroy all trace of him, as it says "Remember what Amalek did to you... you shall wipe out the memory of Amalek... you shall not forget".[8] However, if these nations accept peace terms they are not to be killed. Before declaring war we are commanded to offer peace terms, as it says "When you approach a city to make war on it you must call out to it regarding peace".[9] (We are forbidden to do this with Ammon and Moab, as it says "You shall not seek their peace or welfare"10; but if they make peace with us we accept it.) War must not be conducted destructively; for example, it is forbidde n to cut down fruit trees during a siege, as it says "[If you besiege a city many days...] you shall not destroy its trees".[11,d]
In any war an anointed priest is appointed to address the troops [as it says "And when you approach the battle the priest shall come near and speak to the people"].[12] Anyone who married or built a house or planted a vineyard (or the like) within the past year is not required to serve in the army and it is forbidden to conscript him for any community service, as it says "If a man takes a new wife he shall not go out with the army and he shall not be called on for anything; he shall be free in his house for one year".[l3] It is forbidden to fear the enemy, as it says "[Today you are approaching a battle against your enemies;] your hearts shall not be soft, you shall not fear and you shall not tremble and you shall not be in awe before them"[14]; and one who is afraid is not required to serve in the army. Any army encampment must be kept clean; in particular the latrine must be outside the camp and each soldier must carry a spade to take care of his sanitary needs, as it s ays "And you shall have a place outside the camp... and you shall have a spade along with your weapons... and your camp shall be holy".[15] A soldier is permitted to enjoy the spoils of the enemy at the time of victory; but if he wishes to take a woman of the enemy people he must take her into his house and marry her and he is forbidden to sell or enslave her, as it says "If you see in the spoils a woman of beautiful appearance... [you shall take her into your house... and she shall be a wife to you]... you shall not sell her for money; you shall not enslave her".[16,e]
The messiah will be a king descended from David who will lead the people of Israel in the ways of Torah and will gather the exiles and rebuild the Temple. At that time the whole world will serve Ha-Shem; there will be no more hunger or war and everyone will strive only for knowledge of Ha-Shem, as it says "For the earth is filled with knowledge of Ha-Shem".[l7,f]
1. Gen. 9:4
2. Deut. 17:15
3. Deut. 17:16-20
4. Ex. 14:13
5. Deut. 17:16
6. Deut. 28:68
7. Deut. 20:16-18
8. Deut. 25:17,19
9. Deut. 20:10
10. Deut. 23:7
11. Deut. 20:19
12. Deut. 20:2
13. Deut. 24:5
14. Deut. 20:3
15. Deut. 23:13-15
16. Deut. 21:11-14
17. Isaiah 11:9