Here’s an ethical issue and Jewish source response:
Case
When his parents were discussing how much Judaism opposes the killing of human beings, especially the killing of innocent people, Elliot asked them: “If that is so, then how can Judaism ever allow any war to take place since it involves killing people?” Try as they may, Elliot’s parents could not give Elliot a satisfying answer to his question.
Does Judaism allow any type of war or only specific types? If Jews are opposed to killing, how can Judaism ever allow for war?
Answer
[a] It is true that killing another human being is one of the most serious sins in the Torah. If it will help him stay alive, a Jew is required to commit every sin in the Torah – except for murder, sexual impropriety, and idol worship (Sanhedrin 74a). Jewish law did allow for the death penalty, but a court was called “bloddy” if it put more than one person to death every 70 years (Makkot 7a)! So how does Judaism allow war, since killing is such an integral part of it?
[b] The Torah recognizes that sometimes war is a necessary evil, even though people may be killed. If the Torah totally opposed war, the nations of the world might take advantage of the “pacifist” Jews. Nations might feel free to attack, capture, subjugate and/or kill Jews, use their land and natural resources at will, thus depriving the Jewish people of their lifestyle, their values, and their freedom to worship God. In order to prevent such a situation from occurring (both on an individual basis as well as nationally), the Torah allows individuals to kill in self-defense when their lives are threatened (Exodus 22:1). In addition, the Torah provides for a Jewish army in order to maintain the Jewish people’s independence and way of life (Deuteronomy 220. Even the most traditionally “pacifist” country, Switzerland maintains a standing army for the same reasons. However, we will see that a Jewish war comes only as a last resort, and with many conditions.
[c] From the story of the very first Jew, we can see the establishment of the pattern of the Jewish attitude toward war. Abraham was a peace-loving man who invited every stranger to dine with him in his tent (Sotah 10b). Yet when it was absolutely necessary, this man of peace resorted to battle. When his nephew Lot was captured by the enemy in the midst of a thirteen-year world war, Abraham and his men immediately defeated the four kings who were their enemies and ended the war in order to free Lot. However, they refused to take any spoils (Genesis 14:14-24). Thus, Abraham never sought war, but when forced to fight, he did so and was victorious.
[d] In Jewish law, only three types of wars are permitted (Maimonides, Hilchot Melachim 5:1). One war is to fight and destroy the nation of Amalek, whose avowed purpose is to destroy all Jews and Judaism. The second is to destroy the Seven nations who lived in the Land of Israel and represented a lifestyle antithetical to Judaism (these nations no longer exist today). The third is a war for self-defense. Wars for other purposes are forbidden, except under special circumstances. Even when fighting a “Legitimate” war, actual battle and killing are considered a last resort (Maimonides, Hilchot Melachim 6:7).
Joel Grishaver, “You Be the Judge 2”, pgs. 117-119
Used with permission from Joel Grishaver
