The European just war tradition makes a distinction between matters of just resort to war (jus ad bellum) and matters of just means in war (jus in bello). If one compares the just war tradition with ethical systems of other cultures, one is struck by the European concern about jus ad bellum and the lack of interest in the same in other traditions. I compare the ethics of war in two important literary traditions of classical Hinduism with the European just war tradition. Our problem: Why were Europeans so interested in matters of jus ad bellum (in particular the principle of right authority) and why did Hindu writers take so little interest in the same questions? I suggest the following answer. In medieval and early modern Europe there was great interest in jus ad bellum because Europeans had a concept of war that made two important distinctions. The European concept of war distinguished, firstly, war against external enemies from violence against internal enemies and, secondly, public from private violence. Some important studies of the ethics of war have asserted that these two distinctions are universal. I argue, on the contrary, that these two distinctions are unique to Europe. Hindu writers had a fundamentally different concept of war. They did not make the same distinctions. I argue that this conceptual difference explains why Europeans were so concerned about jus ad bellum while Indians were not.