"Gassed" by John Singer Sargent, 1919
"Gassed" by John Singer Sargent, 1919

From the time of Moses to now, what are the rules of war?


Deuteronomy 16:18–21:9

Isaiah 51:12–52:12

What are the rules of war? Although the conduct of war has changed greatly since the time of Moses, many of the moral and practical challenges have remained the same. When is a war justified? And what actions are permitted in war?

In Parashah Shoftim, the Israelites are preparing to conquer the Land of Israel under the leadership of Joshua. This war is a direct command from God. Therefore, Moses prepares them for the war with specific mitzvot (commandments): offer a generous peace to a city if it will surrender and pay tribute, preserve the fruit trees that you encounter in enemy territory and allow soldiers who are engaged to leave their military service to get married.

But for most of the last 2,000 years, the Jewish nation has had little practical need for these laws of war. The Roman Empire crushed the Bar Kochba revolt in 135 CE. In that final campaign, the Roman historian Cassius Dio reported that 580,000 Jewish men were killed and more than 1,000 Jewish communities in Judea were destroyed.

The archeological evidence from this period implies that the Romans perpetrated a nearly complete genocide against the Jews of Judea. Jewish military power was extinguished. After this devastating blow, there was no independent Jewish military force until the formation of the Israel Defense Forces in 1948.

Nevertheless, the Torah is studied for its own sake and not for any practical benefit. In Hebrew, this is called lishma. Even in the absence of Jewish military power, the rules of war were the legitimate focus of Torah study during those 2,000 years of exile. Therefore, the rabbis of the Talmud, as well as medieval Jewish sages, debated and refined the rules of war presented in the Torah.

For example, the Talmud discusses when it is permissible to go to war. There are different categories of war: milhemet mitzvah, a necessary war, as opposed to milhemet reshut, or a war of conquest (optional). Each category of war has its own rules of conduct, which are discussed and debated in the Talmud, tractate Sotah.

The conclusion is that a war specifically commanded by God in the Torah is certainly a milhemet mitzvah and war for the expansion and glory of the state are certainly a milhemet reshut.

But what about a preemptive defensive war? There is a debate between Rabbi Yehuda haNasi and the other sages regarding the status of such a war. R’ Yehuda argues that such a war is a milhemet mitzvah, while the sages disagree and call it a milhemet reshut. This debate has continued down to this day.

Rabbi Abraham Isaiah Karlitz (the Chazon Ish) was a major rabbi in Israel in the mid-20th century. He argues that any war except for a purely defensive war is a milhemet reshut, but if there is an existing state of war due to an enemy’s aggression, even offensive actions could be considered a milhemet mitzvah.

What about the actual conduct of war, for example, humanitarian concern for civilian populations? The medieval authority Rabbi Moses ben Maimon (the Rambam) writes in the Mishneh Torah, his magisterial work of halachah (Jewish law), that a city that surrenders to a Jewish army must accept the Noahide laws, a minimal set of rules that form the basis for a just society.

In a startling humanitarian gesture, Rambam also rules that when a siege is set up against a city, an escape route must be left open for those who wish to flee. This question came up during the Siege of Beirut in 1982. Leading Israeli rabbis of the time had different opinions. Rabbi Shlomo Goren, a leading Zionist rabbi, argued that evacuations during the siege should be allowed. By contrast, Rabbi Shaul Yisraeli considered the First Lebanon War a milhemet mitzvah and therefore argued on those grounds that no evacuations need be permitted by the IDF.

Now, as I write this, Israel is once again trading blows with a belligerent neighbor. There are many pundits who will either support or denounce Israel’s actions based on their own interpretation of Jewish ethics.

However, the above examples demonstrate that the traditional Jewish perspectives on war are complex and multivocal. Those who seek to condemn or support the actions of the IDF based on their personal understanding of Jewish values would be well served by learning more about the rich rabbinic discourses described above, which inform the IDF’s values. Here in America, we can still learn these texts lishma. But in Israel, these issues are literally matters of life and death.

Rabbi Joel Landau
Rabbi Joel Landau

Rabbi Joel Landau is the spiritual leader of Adath Israel in San Francisco. He can be reached at [email protected].