in this section therefore is not, strictly speaking, the circumstances of a Roman province, but the fortunes of a Roman army, and, as most closely connected therewith, the fortunes of the neighbouring peoples and adversaries, so far as these are interwoven with the history of Rome. [Sidenote: Upper and Lower Germany.] The two headquarters of the army of the Rhine were always Vetera near Wesel and Mogontiacum, the modern Mentz, both doubtless older than the division of the command, and one of the reasons for introducing that division. The two armies numbered in the first century four legions each, thus about 30,000 men[63]; at or between those two points lay the main bulk of the Roman troops, besides one legion at Noviomagus (Nimeguen), another at Argentoratum (Strassburg), and a third at Vindonissa (Windisch not far from Zürich) not far from the Raetian frontier. To the lower army belonged the not inconsiderable fleet on the Rhine. The boundary between the upper and the lower army lay between Andernach and Remagen near Brohl,[64] so that Coblenz and Bingen fell to the upper, Bonn and Cologne to the lower military district. On the left bank there belonged to the upper German administrative circuit the districts of the Helvetii (Switzerland), the Sequani (Besançon), the Lingones (Langres), the Rauraci (Basle), the Triboci (Alsace), the Nemetes (Spires), and the Vangiones (Worms); to the more restricted lower German circuit belonged the district of the Ubii, or rather the colony Agrippina (Cologne), those of the Tungri (Tongern), the Menapii (Brabant), and the Batavi, while the cantons situated farther to the west, including Metz and Treves, were placed under the different governors of the three Gauls. While this separation has merely administrative significance, on the other hand the varying extent of the two jurisdictions on the right bank coincides with the varying relations to their neighbours and the advancing or receding of the bounds of the Roman rule conditioned by those relations. With these neighbours confronting them, matters on the lower and on the upper Rhine were regulated in ways so diverse, and the course of events was so thoroughly different that here the provincial separation became historically of the most decisive importance. Let us look first at the development of things on the lower Rhine. [Sidenote: Lower Germany.]