The just war theory is a doctrine, which is related to and at times interchangeable with such concepts as military tradition, military ethics, the doctrines of military leaders, conflict theology, ethical policy-making, and military tactics and strategy. The purpose of the just war doctrine is to attempt to guarantee that a war is morally justifiable through a series of criteria, all of which must be met for a war to be considered just. The criteria are split into two groups: "right to go to war" (jus ad bellum) and "right conduct in war" (jus in bello). The first concerns the morality of going to war, and the second the moral conduct within war. Recently there have been calls for the inclusion of a third category of just war theory known as jus post bellum that is concerned with the morality of post-war settlement and reconstruction. Just war theory postulates that war, while terrible, is made less so with the right conduct. It also assumes that war is not always the worst option. Important responsibilities, undesirable outcomes, or preventable atrocities may justify war. There is a just war tradition, a historical body of rules or agreements that have applied in various wars across the ages. The just war tradition consists primarily of the writings of various philosophers and legal experts through history. This tradition examines both their philosophical visions of war's ethical limits and whether their thoughts have contributed to the body of conventions that have evolved to guide war and warfare.