Lotharii Regnum
Lotharingia resulted from the tripartite division in 855 of the kingdom of Middle Francia, which itself was formed after the threefold division of the Carolingian Empire by the Treaty of Verdun of 843. Conflict between East and West Francia over Lotharingia was based on the fact that these were the old Frankish homelands of Austrasia, so possession of them was of great prestige.