But the conditions of the oath taken by the two kings in 842 were not observed by either. Karl the Bald was a tyrannical and unpopular sovereign, and when he failed in preventing the Norsemen from ravaging all Western France, the nobles determined to set him aside and invite Ludwig to take his place. The latter consented, marched into France with a large army, and was hailed as king; but when his army returned home, and he trusted to the promised support of the Frank nobles, he found that Karl had repurchased their allegiance, and there was no course left to him but to retreat across the Rhine. The trouble was settled by a meeting of the two kings, which took place at Coblentz, in 860. Ludwig the German had also, like his father, serious trouble with his sons, Karlmann and Ludwig. He had made the former Duke of Carinthia, but ere long discovered that he had entered into a conspiracy with Rastitz, king of the Moravian Slavonians. Karlmann was summoned to Regensburg (Ratisbon), which was then Ludwig's capital, and was finally obliged to lead an army against his secret ally, Rastitz, who was conquered. A new war with Zwentebold, king of Bohemia, who was assisted by the Sorbs, Wends, and other Slavonic tribes along the Elbe, broke out soon afterwards. Karlmann led his father's forces against the enemy, and after a struggle of four years forced Bohemia, in 873, to become tributary to Germany. [Sidenote: 876. DEATH OF LUDWIG THE GERMAN.] In 875, the Emperor, Ludwig II. (Lothar's son), who ruled in Italy, died without heirs. Karl the Bald and Ludwig the German immediately called their troops into the field and commenced the march to Italy, in order to divide the inheritance or fight for its sole possession. Ludwig sent his sons, but their uncle, Karl the Bald, was before them. He was acknowledged by the Lombard nobles at Pavia, and crowned in Rome by the Pope, before it could be prevented. Ludwig determined upon an instant invasion of France, but in the midst of the preparations he died at Frankfort, in 876. He was seventy-one years old; as a child he had sat on the knees of Charlemagne; as an independent king of Germany, he had reigned thirty-six years, and with him the intelligence, prudence and power which had distinguished the Carolingian line came to an end. Again the kingdom was divided among three sons, Karlmann, Ludwig the Younger, and Karl the Fat; and again there were civil wars. Karl the Bald made haste to invade Germany before the brothers were in a condition to oppose him; but he was met by Ludwig the Younger and terribly defeated, near Andernach on the Rhine. The next year he died, leaving one son, Ludwig the Stammerer, to succeed him.