III. Having pacified this part of the country, Cæsar turned all his thoughts towards the war with the Treviri and with Ambiorix, the chief of the Eburones. He was, above all, impatient to take a striking vengeance for the humiliation inflicted on his arms at Aduatuca. Knowing well that Ambiorix would not hazard a battle, he sought to penetrate his designs. Two things were to be feared: the first, that Ambiorix, when his territory was invaded, would take refuge among the Menapii, whose country, adjoining that of the Eburones, was defended by woods and vast marshes, and who, alone among the Gauls, had never made an act of submission; the second, that he might join the Germans beyond the Rhine, with whom, as was known, he had entered into friendly relations through the intermediation of the Treviri. Cæsar conceived the plan of first preventing these two eventualities, in order to isolate Ambiorix. Wishing, above all, to reduce to submission the Menapii and Treviri, and carry the war at the same time into the countries of these two peoples, he undertook in person the expedition against the Menapii, and entrusted that against the Treviri to Labienus, his best lieutenant, who had operated against them on several occasions. Labienus, after his victory over Indutiomarus, had continued in his winter quarters with his legions at Lavacherie, on the Ourthe.[449] Cæsar sent him all the baggage of the army and two legions. He marched in person towards the country of the Menapii, at the head of five legions without baggage. He took with him Cavarinus and the Senonese cavalry, fearing lest the resentment of this king against his people, or the hatred which he had drawn upon himself, might raise some disorders, and, following the general direction of Sens, Soissons, Bavay, and Brussels, he reached the frontier of the Menapii. The latter, trusting in the nature of the ground, had assembled no forces, but took refuge in the woods and marshes. Cæsar divided his troops with the lieutenant C. Fabius and the questor M. Crassus, formed them into three columns, and, causing bridges to be hastily constructed, to cross the marshy water-courses, penetrated at three points into their territory, which he ravaged. The Menapii, reduced to extremity, demanded peace: it was granted to them on the express condition that they should refuse all shelter to Ambiorix or to his lieutenants. Cæsar left Commius among them with part of the cavalry to hold them under surveillance, and marched thence towards the country of the Treviri.[450] [Sidenote: Success of Labienus against the Treviri.]