Cæsar had five or six weeks of leisure before the relieving army appeared. The first part of the decisive engagement was marked by a cavalry battle, in which Cæsar’s German horse proved superior to the Gauls. Then a night attack on the inclosing lines was tried and failed. A daylight struggle afterwards took place along the weakest part of the Roman fortifications, Vercingetorix and the relief force making coincident attacks. The Gauls from the outside were driven off by a skilfully delivered movement on their flank, executed by Labienus, which forced them to withdraw, and at the same time Vercingetorix moved back into the city, and soon recognizing his hopeless position, surrendered. The fall of Alesia marks the completion of the Gallic wars. The spirit of the Gauls was broken; there were afterwards various punitive expeditions, but with the collapse of the great rebellion the country became pacified and accepted its position as a Roman dependency. IV THE BREAK WITH POMPEIUS AND THE SENATE Cæsar’s government of Gaul was now drawing to its close. He had added to the Roman dominions a territory larger than the two original provinces assigned to him. The question now was, what next? The precedents on this point were clear enough; they were written large in the lives of other recent conquerors, Marius and Sulla. But the senatorial party had no intention of allowing Cæsar to return to Rome with a free hand; it was to be a struggle between the self-interests of a narrow oligarchy and a clear-headed effort to attain personal control of the machinery of the government. On neither side was regard for legality given much weight. Both Cæsar and the senatorial party used without scruple illegal means; both at the same time claimed hypocritically to represent the side of law and order.