Deuteronomy chapter 20 is the starting point for all Jewish discussions about war. It is part of Moses‘ final speech to the Israelites and is meant to prepare them for the imminent battles with the nations of Canaan (biblical Israel) as well as their future enemies. The chapter includes an assurance of divine support, a list of those exempt from combat, the requirement to offer peace before attacking an enemy, and other rules of war.
The rabbis of the Mishnah (Sotah 8:7; Sanhedrin 1:5) later elaborated on these rules and in doing so distinguished between two types of wars: commanded wars (milhemet mitzvah) and permitted wars (milhemet reshut).
Though there is some ambiguity on the matter, generally speaking, commanded wars refer to wars against the seven nations that originally inhabited Canaan and against Amalek (the nation that attacked the Israelites as they departed Egypt). Permitted wars are expansionary wars undertaken by Jewish kings to secure their boundaries or increase their glory.
According to almost all traditional authorities, the category of commanded wars is no longer relevant. The seven nations of Canaan, as well as Amalek, are considered extinct or unidentifiable. In addition, commentators such as Nahmanides (1194-1270) believed that even the seven nations were only to be fought if they retained their idolatrous practices. This further neutralizes the possibility of invoking a commanded war, as Islam (according to Maimonides [1135-1204]) and Christianity (according to the Me’iri, Rabbi Menahem ben Solomon, [1249-1316]) are not idolatrous religions.
That being said, Nahmanides ruled that there is an existing commandment to conquer the land of Israel. There have been many commentators, however, who have interpreted this ruling as a call to conquer the land by settling it, as oppose to militarily capturing it.
As scholar Michael Walzer points out, distinguishing between commanded and permitted wars is very different than distinguishing between just and unjust wars. In addition, for close to two thousand years, Jews did not have the ability to fight their own wars. Thus many questions of morality (i.e., jus ad bellum, the ethics of starting a war, and jus in bello, the ethics of battlefield conduct) are under-discussed in Jewish tradition.
The issue of attacking noncombatant civilians (tohar ha’neshek — “purity of arms” — as it is called in Israeli military discourse), for example, is virtually ignored in the Jewish legal tradition (though the second-century Jewish philosopher Philo does mention a prohibition against such conduct). That being said, it is clear that ethical considerations were part of the development of Jewish laws of war.
One of the most striking such laws is the prohibition on besieging a city on all four sides. One side of a city must be left open to allow people to flee. This virtually negates the possibility of siege warfare, and indeed, according to some authorities, is the equivalent of forbidding attacks on civilians. Anyone who does not flee an attacked city can be considered a combatant.
Though defensive wars are not mentioned in Deuteronomy 20, the rabbis of the Talmud permitted — and, indeed, probably required — such battles when Jewish lives are at stake.
The reason for allowing defensive wars is not so clear. Some want to connect it to the biblically commanded obligation of individual self-defense, later summed up by the Talmud (Sanhedrin 72a) as, “If someone comes to kill you, get up early in the morning to kill him first.” Other scholars object to this rationale. J. David Bleich has several problems with citing this as a source for communal self-defense, including the fact that individual self-defense is not justified if it puts innocent bystanders in danger, something war inevitably does.
Preemptive self-defense (i.e., attacking an enemy in anticipation of an attack) is much more controversial. The Talmud (Sotah 44b) seems to provide precedence for this type of military activity, referring to a war for, “diminishing the heathens so that they do not march against them.” Interestingly, however, Maimonides did not codify this ruling. Nonetheless, most authorities allow preemptive strikes in situations where it is clearly in self-defense.
Today, of course, the justifiability of war — particularly preemptive war — is rarely clear-cut. And as Elliot Dorff notes, “even those who have the same Jewish perspective on the general issue of preemptive war may disagree as to whether a given preemptive action is legitimate.”
Pronounced: TALL-mud, Origin: Hebrew, the set of teachings and commentaries on the Torah that form the basis for Jewish law. Comprised of the Mishnah and the Gemara, it contains the opinions of thousands of rabbis from different periods in Jewish history.