This paper considers the use of the principle of proportionality in existential war. It explores the development of the idea of proportionality in war from antiquity onwards, through the writings of Augustine and Aquinas (as a component of the idea of a Just War); the Valladolid debate on the conquest of the Americas, and relevant discussion at the School of Salamanca later in the sixteenth century. It also discusses Machiavelli's use of Livy in forming his ideas on the use of disproportionate power in politics. The paper is intended for formal publication in 2017. it is in four sections.
1 Existential War
2 War in Antiquity
3 Discussing the Concept of the Just War
4 The Problem of Modern Existential War