Eight years before his death, Charles the Great made his three sons kings.[319:1] This act would have proved fatal to the Empire. Charles must have known from the writings of Gregory of Tours, the dangers of such an arrangement. The division made among his sons was unnatural, because it lacked unity in race and territory, but the death of Charles and Pepin, the eldest and second sons, prevented imperial suicide. Charles the Great then solemnly crowned the surviving son, Louis, as Emperor in 813. Louis the Pious (814-840) sought to preserve both the Carolingian practice of division and the integrity of the Empire. At Aachen, in 817, to prevent the Empire's being "broken by man lest thereby a scandal, to the Holy Church might arise," Louis made his eldest son, Lothair, co-Emperor, and, with the consent of the people, crowned him.[319:2] The younger sons were made kings but _sub seniore fratre_. Their territorial districts were clearly defined and elaborate instructions were given about their various relations.[319:3] In 819, Louis married again and soon a fourth son, Charles the Bald, appeared to complicate matters (823). Louis then made a new division of the Empire in order to provide for the new claimant.[319:4] A long list of territorial changes, and disgraceful, ruinous, internecine wars resulted. Louis the Pious died in 840, and was succeeded by Lothair as sole Emperor. His brothers, Louis and Charles (Pepin was now dead), rebelled against him and forced him to restrict his possessions to Italy and a narrow strip running from Italy to the North Sea (843). But Lothair, tired of the cares of this life retired to a monastery in 855 after dividing his imperial territory among his three sons. As a result of the Carolingian policy of division, the Empire so skilfully constructed by Charles the Great, was almost destroyed. Division of rule meant division of resources. The successors of Charles the Great were men of inferior ability. His son, Louis the Pious, was a weak, easily influenced ruler and completely under the thumbs of the clergy. He made some noble efforts to reform the court, but only aroused the enmity of the aristocracy. Lothair, Louis II., and Charles the Bald were Emperors of as short-sighted a policy and of as little ability. Civil wars were almost incessant; nobles held in subjection by the great Charles reasserted their independence; the Northmen,[320:1] Slavs, Hungarians[320:2] and Saracens began to make disastrous inroads; imperial laws were disregarded; and by the end of the ninth century, the Empire of Charles the Great was little more than an empty title hardly worth fighting for.[320:3]