844 he compelled the Obotrites to accept his authority and put their prince, Gozzmovil, to death. Thachulf, Duke of Thuringia, then undertook campaigns against the Bohemians, Moravians, and other tribes, but was not very successful in resisting the ravaging Vikings. Conflicts with Charles the Bald In 852 Louis sent his son Louis the Younger to Aquitaine, where nobles had grown resentful of Charles the Bald's rule. The younger Louis did not set out until 854, and returned the following year. Starting from 853 Louis made repeated attempts to gain the throne of West Francia, which, according to the Annals of Fulda (Annales Fuldenses), the people of that country offered him in their disgust with the cruel misrule of Charles the Bald. Encouraged by his nephews Peppin II and Charles of Provence, Louis invaded in West Francia in 858. Charles the Bald could not even raise an army to resist the invasion and fled to Burgundy. Later that year Louis issued a charter dated "the first year of the reign in West Francia." However, treachery and desertion in his army, and the continued loyalty of the Aquitanian bishops to Charles the Bald, brought about the failure of the whole enterprise. As such on 7 June 860 at Koblenz, both Louis and Charles made public vows to uphold the peace. After the emperor Lothair I died in 855, Louis and Charles for a time cooperated in plans to divide Lothair's possessions between themselves, the only impediments to this being Lothair's sons and heirs—Lothair II (who received Lotharingia), Louis II of Italy (who held the imperial title and the Iron Crown of Lombardy) and Charles of Provence. In 868 at Metz Louis and Charles agreed to partition Lotharingia. When Lothair II died in 869, Louis was lying seriously ill, and his armies were engaged in a war with the Moravians. Charles the Bald quickly seized Lothair's lands, but Louis, having recovered, compelled him by threat of war to agree to the Treaty of Meerssen, which divided Lothair's lands among all the claimants. Divisio regni among the sons The later years of Louis the German were troubled by rebellions of his sons. The eldest, Carloman of Bavaria, revolted in 861 and again two years later. This was followed by the second son Louis the Younger, who was joined by his brother Charles the Fat. In 864 Louis was forced to grant Carloman the kingdom