THIS book has grown rather than been deliberately made. For the last fifty years I have lectured off and on, and for many of them on rather than off, on the relations of the European States to each other during the eighteenth century. And I took one part of those relations as the subject of my Ford Lectures in the University of Oxford. My experience as a teacher has convinced me that the darkest spot in the history of Europe in the eighteenth century is the period of the war of the Austrian Succession. Its military side may have been adequately treated by Carlyle and other writers, but I do not profess to be a military historian. But the political side of the war has been left, at any rate in this country, in great obscurity. The most notable attempts to penetrate this obscurity have been made by Arneth, in his monumental work on Maria Theresa, and by the Duc de Broglie, in the long series of volumes which he has devoted to this period. But Arneth was almost exclusively dependent upon the Austrian archives, among which he passed his life; and Broglie, though he had a larger outlook, was imperfectly acquainted with English sources. I omit the Prussian historians because they have helped to mislead the student by concentrating attention upon those periods of the war in which their hero, Frederick the Great, was a protagonist. No Englishman, since Archdeacon Coxe, had made anything like a thorough study of foreign policy during this decade, and much has been discovered since the days of the industrious Archdeacon.