In 16, when governor of Gaul, he was defeated by the Sigambri (Sygambri), Usipetes and Tencteri, German tribes who had crossed the Rhine.
In 55 B.C. certain German tribes, the Usipetes and Tencteri, crossed the lower Rhine, and invaded the modern Flanders.
Certain tribes, such as the Tencteri, were famous for their horsemen, but the Germani in general preferred to fight on foot.
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.