Louis, called "the Pious," because the latter part of his life was spent in mourning his outrageous betrayal, mutilation, and murder of his own nephew, whose rivalry he feared, succeeded his father, Charlemagne. He was succeeded again by his three sons, Lothair, Pepin, and Louis by his first wife, and Charles, who was his favorite son, by his second wife. He had already divided the great heritage left him by Charlemagne between his three sons Lothair, Pepin, and Louis; but now he wished to make another division into four parts, to make room for, and to give a kingdom to, his son Charles by his second wife. The three elder sons revolt against their father, and his last years are spent in vain attempts to reconcile his quarrelsome children. At his death war breaks out. Pepin dies, leaving, however, a son Pepin to inherit his kingdom of Aquitaine. Louis and Charles attempt to take his kingdom from him, his uncle Lothair defends him, and at the great battle of Fontenay (841) Louis and Charles defeat Lothair. Lothair gains the adherence of the Saxons, and Charles and Louis at the head of their armies confirm their alliance, and at Strasburg the two armies take the oath of allegiance: the followers of Louis took the oath in German, the followers of Charles in French, and this oath, the words of which are still preserved, is the earliest specimen of the French language in existence. In 843 another treaty signed at Verdun, between the two brothers Lothair and Louis and their half-brother Charles, separated for the first time the Netherlands, the Rhine country, Burgundy, and Italy, which became the portion of Lothair; all Germany east of this territory, which went to Louis; and all the territory to the west of it, which went to Charles. Germany and France, therefore, by the Treaty of Verdun in 843, became distinct kingdoms, and modern geography in Europe is born.