The monastery of Monte Cassino, founded by St. Benedict in the sixth century, was the cradle of Western monasticism. It became one of the vital centers of culture and learning in Europe. At the height of its influence, in the eleventh and early twelfth centuries, two of its abbots (including Desiderius) and one of its monks became popes, and it controlled a vast network of dependencies--churches, monasteries, villages, and farms--especially in...