Just War theory (jus bellum iustum) is a doctrine, also referred to as a tradition, of military ethics studied by theologians, ethicists, policy makers, and military leaders. The purpose of the doctrine is to ensure 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: ‘the right to go to war’ (jus ad bellum) and "right conduct in war" (jus in bello).