European feudal society during the eleventh and twelfth centuries was organized for war, yet little is known of the ability displayed by the knights and their leaders in military operations. The most accessible sources of information, for students and general readers alike, are histories of the art of war which survey the whole medieval period. Since no one scholar can hope to master the sources for the history of so great a subject through a millennium, such works need to be rooted in the more limited researches of specialists. Attempts at synthesis have been only partially successful because such special studies are comparatively few in number. More are needed for the better understanding of medieval warfare, and therefore of an important aspect of medieval life, and that need is the justification for this book. Many historians of the art of war have recognized the interest of its subject, and have written on it with distinction; but their treatment has been brief, and none has been able to undertake a study in the detail now attempted.

There is a further difference. Most of these scholars have confined their interest in war to events on the battlefield, and have looked no further. As a result military history too often stands unnaturally isolated from other fields of historical study.