While Cæsar found so great difficulties before him, Lucterius,[463] who had been sent by Vercingetorix to the Ruteni, brings them over to the alliance with the Arverni, advances towards the Nitiobriges and the Gabali, from whom he receives hostages, and, at the head of a numerous army, threatens the Province in the direction of Narbonne. These events made Cæsar resolve to proceed to that town. His arrival put an end to people’s fears. He placed garrisons among the peoples who bordered on the territory of the enemy, the Ruteni of the left bank of the Tarn (_Ruteni provinciales_), the Volcæ Arecomici, the Tolosates, and near Narbonne. At the same time, he ordered a part of the troops of the province, and the re-enforcements which he had brought from Italy, to unite on the territory of the Helvi, which bordered upon that of the Arverni.[464] Intimidated by these dispositions, Lucterius did not venture to engage himself in the midst of these garrisons, and retired. This first danger averted, it was important for Cæsar to prevent Vercingetorix from raising other peoples, who might perhaps be inclined to follow the example of the Bituriges. By invading the country of the Arverni, Cæsar might hope to draw the Gaulish chief into his own country, and thus remove him from those where the legions were wintering. He proceeded, therefore, to the country of the Helvi, where he joined the troops who had just concentrated there. The mountains of the Cévennes, which separated this people from the Arverni, were covered with six feet of snow; the soldiers opened a passage by dint of labour. Advancing by Aps and Saint-Cirgues, between the sources of the Loire and the Allier (_see Plate 19_), Cæsar debouched on Le Puy and Brioude. The Arverni, at this season, the most rigorous of the year, believed themselves defended by the Cévennes, as by an insurmountable wall: he fell upon them unexpectedly, and, in order to spread still greater terror, he caused the cavalry to scour the country far around.