Judaic thought on the role of war in the history of the children of Israel begins with the biblical narratives that record a variety of belligerencies in which God is often depicted as the one who leads the Hebrews in battle, protects them from their enemies, and makes them victorious over other armies. Thus, during the initial phase of the exodus from Egypt, when the people were terrified by the approach of the Egyptian army, Moses sought to calm them by assuring them that the Lord will fight for you (Ex. 14:14), which he repeated when he sought to calm their concerns by again assuring them: The Lord your God who goeth before you, He shall fight for you (Deut. 1:30). These assurances clearly were not intended to be taken literally. The metaphor of God as their warrior had multifaceted connotations for a people who knew or at least perceived themselves to be smaller and weaker than the nations with which they would have to contend in order to establish themselves in the land divinely promised to their ancestors. The metaphor provided the children of Israel with a sense of security; informing them that they were chosen for freedom by an all-powerful God who would continue to support them even in the face of apparently overwhelming challenges. The present study focuses primarily on a number of biblical narratives selected because they each reflect the basic issues of reason and morality that relate to the conduct of warfare throughout human history, as understood in Judaic thought. In each case, the context will be described to the extent necessary to evaluate the rationale and consequences, both intended and unintended, of the resort to armed conflict. The study then addresses the efforts, in the post-biblical rabbinic period, to amplify and codify the rules pertaining to the making and conduct of war and peace, a process that continues in Judaic thought to the present day, when such decisions, after a lapse of two millennia, once again confront autonomous decision-makers in the modern State of Israel.