The Principles of Jus Ad Bellum
The other principles central to jus ad bellum are right authority, right intention, reasonable hope, proportionality, and last resort.
The principle of right authority suggests that a war is just only if waged by a legitimate authority. Such authority is rooted in the notion of state sovereignty and derived from popular consent. Even if their cause is just, individuals or groups whose authority is not sanctioned by society members cannot justifiably initiate war. It is important to note, however, that corrupt governments that rule arbitrarily and unjustly may not warrant the allegiance of the populace. In these cases, state sovereignty disintegrates, and individuals may have a right to declare war in order to defend themselves from an illegitimate government. Struggles for independence by distinct communities that are ready and able to determine the conditions of their own existence may sometimes be justified.
According to the principle of right intention, the aim of war must not be to pursue narrowly defined national interests, but rather to re-establish a just peace. This state of peace should be preferable to the conditions that would have prevailed had the war not occurred. Right intention is tied to the conditions of jus in bello, (justice in war) and forbids acts of vengeance and indiscriminate violence. Because the proper object of wars is a better state of peace, just wars are limited wars. Unconditional surrender is often thought to violate the principle of right intention because it deprives a nation of its rights and sovereignty, and in effect destroys it. Nevertheless, in cases such as Nazism, where a government regime poses a threat to the very existence of entire peoples, the conquest and reconstruction of an enemy state may be a legitimate military goal.
Here, however, it is important to note that securing peace often overlaps with the protection of self-interest. For example, if the only way to secure peace is to annex a belligerent neighbor's territory, proper intention is linked to pursuing self-interest. Other proper intentions for war, such as defending an oppressed group and securing its freedom, may be abandoned because such a war is deemed too costly.
In addition, just wars must have a reasonable chance of success. According to the principle of reasonable hope, there must be good grounds for believing that the desired outcome can be achieved. Arms may not be used and deaths incurred in a futile cause or when the probability of success is very low. This principle involves weighing the costs and benefits of waging war, and "emphasizes that human life and economic resources should not be wasted" on war efforts that are certain to fail. However, some note that in some cases it is necessary as a matter of moral principle to stand up to bullying forces even if there is little chance of success. For the sake of national pride, fights that are seemingly hopeless may sometimes be justifiably undertaken.
The principle of proportionality stipulates that the violence used in the war must be proportional to the attack suffered. The means should be commensurate with the ends, as well as be in line with the magnitude of the initial provocation. States are prohibited from using force not necessary to attain the limited objective of addressing the injury suffered. For example, if one nation invades and seizes the land of another nation, this second nation has just cause for a counter-attack in order to retrieve its land. However, if this second nation invades the first, reclaims its territory, and then also annexes the first nation, such military action is disproportional. In addition, the minimum amount of force necessary to achieve one's objectives should be used. Thus, the principle of proportionality overlaps with jus in bello, the conditions for how war should be fought.
Finally, the principle of last resort stipulates that all non-violent options must be exhausted before the use of force can be justified. A just war can only be waged once all other diplomatic avenues have been pursued.
By Michelle Maiese
 Don Hubert and Thomas G. Weiss et al. The Responsibility to Protect: Supplementary Volume to the Report of the International Commission on Intervention and State Sovereignty. (Canada: International Development Research Centre, 2001), 139. <http://books.google.com/books?id=31qFeSkSb5IC>.
 Alex Moseley," Just War Theory," in The Internet Encyclopedia of Philosophy (2009, accessed February 3, 2003). <http://www.utm.edu/research/iep/j/justwar.htm>.
 Michael Walzer, Just and Unjust Wars: A Moral Argument with Historical Illustrations, 2nd Edition. (New York: Basic Books, 1997), 44. 4th Edition (2006) available here, cit 93.
 Walzer, op. cit 121.
 Walzer, op. cit 114.
 Hubert and Weiss, et al., 139.
 Hubert and Weiss, et al., 139