Towards the end of Caesar's Gallic War, Rome had reached the Rhine. Since the campaigns under Emperor Augustus (15 B.C.), larger troop contingents were stationed along the river, with focal points around Mogontiacum/Mainz and in northern Switzerland. After the Battle of the Teutoburg Forest (9 AD), when the attempt to occupy all of Germania had failed, the Lower Rhine remained the frontier of the empire's territory until Late Antiquity. East...