Louis II became sole Emperor in 855, when his father died. His uncles, Charles the Bald and Louis the German, did not dispute his claim because they were too busy fighting each other.
Louis soon conquered most of the lands that his father had willed to Louis' brothers, Lothar II and Charles of Provence.
Louis' "third man in the kingdom" was Landolf of Capua. Landolf encouraged Louis to drive the Arabs out of Italy, while at the same time he was encouraging the Arabs to attack Italy. His treachery, combined with his interest in magic and astrology, made him the basis for the character of the evil magician, Klingsor, in Wagner's opera of the Holy Grail, Parsifal.
In 866, Louis went to war to drive the Arabs from Italy. With the help of the Byzantine Navy, he conquered the Arab stronghold of Bari in 871, but Arab forces remained in Italy until 884.
In 877, Louis II died without a male heir. His uncle, Charles the Bald became the Holy Roman Emperor.
In 890, Emperor Louis II's Queen Engelberge, died. She is said to have campaigned with him, negotiated peace for Louis with his uncles, and to have reconciled him with Pope Nicholas I. Apparently, Louis retained his taste for strong-willed women.