This essay critically examines the just war theory, exploring its historical development, ethical foundations, and practical application in the context of 20th and 21st-century warfare. The introduction establishes the concept of war and the essay's central argument regarding the redundancy of just war principles in contemporary conflicts. The main body delves into the history of just war theory, tracing its roots from Augustine and Aquinas, and analyzing its core components: Jus Ad Bellum, Jus In Bello, and Jus Post Bellum. The essay assesses the theory's applicability by examining its role in historical conflicts, like World War I and the US Civil War, and discussing how modern warfare techniques and evolving moral considerations have challenged its relevance. The essay considers nuclear weaponry and the complexities of modern warfare. The conclusion synthesizes the arguments, offering a final perspective on the extent to which the just war theory continues to provide a useful framework for understanding and evaluating the ethics of war.