The Just War tradition has been seen as a leading perspective on the ethics of war since the writings of St Augustine were rearticulated by Thomas Aquinas. It attempts to provide a framework which validates just conflicts, whilst at the same time applying limits so as to prevent unrestrained warfare. Today, its core principles can be divided into two broad categories: ‘jus ad bellum’ (just resort to war) and ‘jus in bello’ (just conduct in war). For a war to be just, numerous criteria must be satisfied within these categories.