Louis, who is also called _Le Débonnaire_, counts as Louis I., king of France. See _Annales Fuldenses_; _Annales Bertiniani_; Thegan, _Vita Hludowici_; the _Vita Hludowici_ attributed to Astronomus; Ermoldus Nigellus, _In honorem Hludowici imperatoris_; Nithard, _Historiarum libri_, all in the _Monumenta Germaniae historica_. _Scriptores_, Bände i. and ii. (Hanover and Berlin, 1826 fol.); E. Mühlbacher, _Die Regesten des Kaiserreichs unter den Karolingern_ (Innsbruck, 1881); and _Deutsche Geschichte unter den Karolingern_ (Stuttgart, 1886); B. Simson, _Jahrbücher des fränkischen Reichs unter Ludwig dem Frommen_ (Leipzig, 1874-1876); and E. Dümmler, _Geschichte des ostfränkischen Reiches_ (Leipzig, 1887-1888). (A. W. H.*) LOUIS II. (825-875), Roman emperor, eldest son of the emperor Lothair I., was designated king of Italy in 839, and taking up his residence in that country was crowned king at Rome by Pope Sergius II. on the 15th of June 844. He at once preferred a claim to the rights of an emperor in the city, which was decisively rejected; but in 850 he was crowned joint emperor at Rome by Pope Leo IV., and soon afterwards married his cousin, Engelberga, a daughter of King Louis the German, and undertook the independent government of Italy. He took the field against the Saracens; quashed some accusations against Pope Leo; held a diet at Pavia; and on the death of his father in September 855 became sole emperor. The division of Lothair's dominions, by which he obtained no territory outside Italy, aroused his discontent, and in 857 he allied himself with Louis the German against his brother Lothair, king of Lorraine, and King Charles the Bald. But after Louis had secured the election of Nicholas I. as pope in 858, he became reconciled with his brother, and received some lands south of the Jura in return for assistance given to Lothair in his efforts to obtain a divorce from his wife, Teutberga. In 863, on the death of his brother Charles, Louis received the kingdom of Provence, and in 864 came into collision with Pope Nicholas I. over his brother's divorce. The archbishops, who had been deposed by Nicholas for proclaiming this marriage invalid, obtained the support of the emperor, who reached Rome with an army in February 864; but, having been seized with fever, he made peace with the pope and left the city. In his efforts to restore order in Italy, Louis met with considerable success both against the turbulent princes of the peninsula and against the Saracens who were ravaging southern Italy. In 866 he routed these invaders, but could not follow up his successes owing to the want of a fleet. So in 869 he made an alliance with the eastern emperor, Basil I., who sent him some ships to assist in the capture of Bari, the headquarters of the Saracens, which succumbed in 871. Meanwhile his brother Lothair had died in 869, and owing to his detention in southern