The just war theory is a doctrine, also referred to as a tradition, of military ethics that aims to ensure that a war is morally justifiable through a series of criteria, all of which must be met for a war to be considered just. It has been studied by military leaders, theologians, ethicists and policymakers. The criteria are split into two groups: jus ad bellum and jus in bello. There have been calls for the inclusion of a third category of just war theory dealing with the morality of post-war settlement and reconstruction. The just war theory postulates that war, while it is terrible but less so with the right conduct, is not always the worst option, but justifiable when justice is an objective of armed conflict. Important responsibilities, undesirable outcomes, or preventable atrocities may justify war.