This book is first of all an essay of political philosophy. This book is clear, straightforward, and comprehensive. It truly addresses the issue announced in the title. At the heart of this book is a comprehensive exposition of classic Just War doctrine going back to St. Augustine of Hippo and St Thomas Aquinas with a strong argument that these ancient principles have stood the test of time and should still be determinant of the ethics of warfare. Starting from the postulate that "preparing for war is the primary function of politics and combining the reflection of the officer and the Christian, his ambition is to "make people rediscover the (Christian) principles which should guide political action on the subject of war.