The concept of the just war poses one of the most important ethical questions to date. Can war ever be justified and, if so, how? When is a cause of war proportional to its costs and who must be held responsible? The monograph demonstrates that the necessary moral evaluation of these questions is not restricted to the philosophical moral and political discourse. This analysis of Shakespeare's plays, which focuses on the histories, tragedies and Roman plays in chronological order, brings to light that the drama includes an elaborate and complex debate of the ethical issues of warfare. The plays that feature in this analysis range from to and they are analysed according to the three Aquinian principles of legitimate authority, just cause and right intention. Also extending the principles of analysis to more modern notions of responsibility, proportionality and the jus in bello-presupposition, this monograph shows that just war theory constitutes a dominant theoretical approach to war in the Shakespearean canon.