In an age of terrorism, guerilla and total warfare the medieval doctrine of Just War needs to be re-defined. Moreover, issues of legitimacy, efficacy and morality should not be confused. Legitimacy is conferred by institutions. Not all morally justified wars are, therefore, automatically legitimate. Frequently the efficient execution of a battle plan involves immoral or even illegal acts.
As international law evolves beyond the ancient percepts of sovereignty, it should incorporate new thinking about pre-emptive strikes, human rights violations as casus belli and the role and standing of international organizations, insurgents and liberation movements.
Yet, inevitably, what constitutes "justice" depends heavily on the cultural and societal contexts, narratives, mores, and values of the disputants. Thus, one cannot answer the deceivingly simple question: "Is this war a just war?" - without first asking: "According to whom? In which context? By which criteria? Based on what values? In which period in history and where?"
Being members of Western Civilization, whether by choice or by default, our understanding of what constitutes a just war is crucially founded on our shifting perceptions of the West.