This book is an interpretation of one of the great works of western literature, Thucydides' History. The scholarship on Thucydides may cause despair and fatigue by its sheer mass. If I have ventured to add this book to that mass, it is with the conviction that despite – or rather, because of – all of the previous work, original and useful insights are still possible, and always will be. It is a sign of Thucydides' greatness that, despite the difficulty of his language and thought, the generations have not ceased reading and writing about him with sustained passion. His text, unfinished as it is, still serves as a basic textbook for history and political science, as a reference point for political controversy of the present day and as a vehicle for travel to the higher realms of historical understanding and speculation. The sum of generations of comment and discovery approaches, yet never overtakes, the masterworks of style and thought.

Every generation of course has its peculiar biases. It may be that the past decade, or even the past century, has made understanding the difference between war and civil war more urgent, yet at the same time it has also made that difference more vague, attenuated and insignificant. Thucydides' reflections on internal war, from our perspective, seem to point to that conclusion.