This study had its inception a number of years ago in a doctoral dissertation prepared under the direction of the late Professor Carl Stephenson at Cornell University. The dissertation, which fortunately was never published, was concerned with the role of the castle in the military history of England from the Conquest to the end of the reign of Henry IL But I soon found that the castle, though probably the most important military innovation of the Normans, could not be studied intelligently without reference to other military developments. So the scope of my inquiry was eventually broadened to include the whole history of warfare in England from the landing of Duke William in September 1066 to the death of Henry II in July 1189. It had long been suspected that the old notion of an "age of cavalry," at least as it applied to England, needed modification, and the work of C. Warren Hollister, Michael Powicke, Robert S. Hoyt, and others has confirmed this suspicion. But these scholars have confined their efforts largely to the institutional aspect of military history — to the means by which English kings raised their armies, rather than to the uses made of the troops once they had been mustered. In fact, no such survey exists, and in the current debate over the history of English and Anglo-Norman military institutions, a detailed examination of warfare in the Norman and early Angevin periods might help to clear the air. Much to my regret, Professor C. Warren Hollister's "The Military Organization of Norman England" was published too late to be taken into consideration; but it is gratifying to note that we are of the same mind on many a controversial issue. ("Preface")