In 16, when governor of Gaul, he was defeated by the Sigambri (Sygambri), Usipetes and Tencteri, German tribes who had crossed the Rhine.
Beyond these were found the Frisians, a people of German origin, who gave their name to the territory between the Rhine and the Ems. Of the other tribes the best known are the Caninefates, Chauci, Usipetes, Sicambri, Eburones, Menapii, Morini and Aduatici.
In 55 B.C. certain German tribes, the Usipetes and Tencteri, crossed the lower Rhine, and invaded the modern Flanders.
On the right bank of the Rhine, between the Main and the Lahn, were the settlements of the Mattiaci, a branch of the Germanic Chat ti, while farther to the north were the Usipetes and Tencteri.
Among these we may mention the campaign of his first year of office, 58 B.C., against the German king Ariovistus, who led the movement in Alsace, and that of 55 B.C. in which he expelled the Usipetes and Tencteri who had crossed the lower Rhine.
Beyond them were the Tencteri, probably about the basin of the Lahn, and the Usipetes about the basin of the Ruhr.