Bellum iustum or the Just War Theory is a military ethics doctrine derived from Episcopal philosophy of the Roman Catholic Church. As studied today, the Just War Theory is considered hugely informed by the Christian understanding of the justifications of wars of invasion. In ethicist literature as in moral theology and policy making, the Just War Theory is associated with the belief that conflicts can be justified under certain philosophical, political and religious criteria. This paradigm dates back to the times of Marcus Tullius Cicero, a Roman statesman, philosopher, lawyer, theorist and constitutionalist. The connection of the theory to medieval Christian theory and particularly, contemporary Catholicism is in the works of Thomas Aquinas and Aurelius Augustinus Hipponensis (Gutman & Rieff, 2000). The former, also called Thomas of Aquin was an Italian Dominican priest, a theologian and a philosopher. The latter, also called St. Augustine, Blessed Augustine or Augustine of Hippo, was a onetime Bishop of Hippo Regius, a philosopher and theologian. This paper describes the tenets of the just war theory derived from the works of these philosophers and the utility of the theory within contemporary warfare. Specific focus is on the justification of the US invasion of Iraq and the consequences thereof.
In the works of these three philosophers, the Just War Theory took a Christian connotation of the Roman Empire’s view of warfare. The Christian understanding of provocation to war and the ethics of warfare shifted to strong beliefs in a jurisdiction’s duty or right to fight for a course that is considered just. This paradigm shift abandoned the oft strict pacifism that characterized relations in pre-medieval history of human civilization. In the works of the mentioned moral thinkers, the belief that all international disputes could be settled by arbitration was discarded for a more pragmatic perspective that was based on four tenets. To proceed into war, the aggressor must have caused a grave, certain and lasting damage to the defender or his interests. In the face of such aggression, all alternatives of causing an end should have been proved ineffective or unworkable. Third, prospects of success in the face of invasion should be clear. Finally, if the defender must use arms, such a use may not produce disorders or evils equal or graver than the aggressors.
So listed, the application of these tenets in instances where force must be used to suppress aggression, in most times, decries of ethical/moral justifications. The muscle of modern artilleries of war, for instance, weighs very heavily when such conditions are evaluated. Essentially, however, the balance between moral detestation of war and the necessity of war is often reachable to justify war under these tenets. In forceful warfare, the evaluation must take into consideration the moral permissibility of resorting into armed conflict. Whereas a lasting gravity of aggression can easily be ascertained, the distinction between an unjustifiable and a justifiable application of organized armed forces because an “alternative” avenue is unavailable is often debatable. The Middle East crisis is an example in which peace has often been traded off as an alternative to missile attacks between Israel and the Gaza strip by debaters. The prospects of success may often be clear too, but as armed conflicts have always projected, the attainability of such an end may be very uncertain. In addition, how to use the same in a manner that does not surpass the magnitude of the aggression is often debatable. It is often unattainable because aggressors in such armed conflicts do not lie back and watch as they are attacked. The scale of destruction in armed invasion is often higher than that of the aggression.
As the US invasion of Iraq suggests, the practicability of the Just War Theory is relatively contentious. In this case, two dimensions of the theory have been explored- jus ad bellum which defines the justness of going to war and jus in bello which defines the justness of conduct of the warring parties (Enemark & Michaelsen, 2005). When the “Coalition of the Willing” invaded Iraq in March 2003, the understanding under jus ad bellum was that Saddam Hussein was harboring weapons of mass destruction and that the potential of using such weapons would be more grievous than if they were intercepted and destroyed (Enemark & Michaelsen, 2005). All alternatives for ending the purported use of such weapons were also proving futile and so the US found justification in attacking Iraq then.
Under jus in bello, however, there has never been a practical justification of using such immense force, over and above what Saddam did or intended to do. In the framework of just war theory, the US campaign is therefore blatantly unjust. One reason for the invasion- the just cause of self-defense- was certainly assumed on intelligence whose foundations were largely uncertain. The US found no links between terrorism and Saddam’s harboring of such weapons. Justifying the cause of humanitarian intervention has never stood alone in Iraq’s case because prior to the invasion, there were no major humanitarian suffering that demand an action as urgent as was assumed by the US. Because the intended course may have been blurred by Saddam’s resistance, criteria three and four were definitely violated. In the end, the US succeeded in ousting Saddam, failed to find the weapons of mass destruction and planted a seed of mistrust in Americans and non-Americans alike about the motives of the war. Essentially, the justification that the US under George W. Bush may have found in the Just war theory initially was eroded when excessive force was used to oust Saddam.

References
Enemark, C., and Michaelsen, C. (2005). Just War doctrine and the invasion of Iraq. Australian Journal of Politics and History. 51(4), 545–563.
Gutman, R., and Rieff, D. (2000). Crimes of war: What the public should know. New York, NY: W. W. Norton & Company.