Lothar retired Italy to his eldest son Louis II in 844, making him co-emperor in 850. By the Treaty of Prüm (855), Lothar divided his kingdom into three parts: the Itlian territory already held by Louis remained his, the territory of the former Kingdom of Burgundy was granted to his third son Charles of Burgundy, and the remaining territory for which there was no traditional name was granted to his second son Lothar II, whose realm was named Lotharingia.
lothar retired italy to his eldest son louis ii in 844 making him co-emperor in 850 by the treaty of prüm (855) lothar divided his kingdom into three parts the itlian territory already held by louis remained his the territory of the former kingdom of burgundy was granted to his third son charles of burgundy and the remaining territory for which there was no traditional name was granted to his second son lothar ii whose realm was named lotharingia