Gallia Belgica was infiltrated by the Germanic Franks from the 4th century, and was abandoned by Rome in AD 406. The territory of what would become Luxembourg by the 480s became part of Merovingian Austrasia and eventually part of the core territory of the Carolingian Empire. With the Treaty of Verdun (843), it fell to Middle Francia, in 855 to Lotharingia and with the latter's division in 959 to the Duchy of Upper Lorraine within the Holy Roman Empire.