The land of "Agri Decumates" that was guarded by this "limes" had to be vacated by the Romans in 260-285 AD. They moved their bases back to the banks of the Rhine and Danube, which were much easier to defend militarily. The exact route of the "limes" along the border between Upper Germania and Raetia has not been fully explored. In the late 4th and early 5th centuries, the Rhaetian Limes was reorganized and divided into three sections. The northern border of "Rhaetia" formed the "pars superior" (upper part), the western border was the "pars media" (central part) with the fortified town of Cambodunum and bases from "Vemania" (Isny im Allgäu) to "Cassilacum" (Memmingen); the "pars inferior" (lower part) was the section between "Castra Regina" (Regensburg) and "Batavis" (Passau).