The History of the Medieval World : From the Conversion of Constantine to the First Crusade

From the schism between Rome and Constantinople to the rise of the T'ang Dynasty, from the birth of Muhammad to the crowning of Charlemagne, this erudite book tells the fascinating, often violent story of kings, generals, and the peoples they ruled.
In her earlier work, The History of the Ancient World, Susan Wise Bauer wrote of the rise of kingship based on might. But in the years between the fourth and the twelfth centuries, rulers had to find new justification for their power, and they turned to divine truth or grace to justify political and military action. Right thus replaces might as the engine of empire.
Not just Christianity and Islam but the religions of the Persians and the Germans, and even Buddhism, are pressed into the service of the state. This phenomenon-stretching from the Americas all the way to Japan-changes religion, but it also changes the state.