The value of the consulship lay in the lucrative provincial governorship to which it would normally lead. On the eve of the consular elections for 59 bce, the Senate sought to allot to the two future consuls for 59 bce, as their proconsular provinces, the unprofitable supervision of forests and cattle trails in Italy. The Senate also secured by massive bribery the election of an anti-Caesarean, Marcus Calpurnius Bibulus. But they failed to prevent Caesar’s election as the other consul.

Caesar now succeeded in organizing an irresistible coalition of political bosses. Pompey had carried out his mission to put the East in order with notable success, but after his return to Italy and his disbandment of his army in 62 bce, the Senate had thwarted him—particularly by preventing him from securing land allotments for his veterans. Caesar, who had assiduously cultivated Pompey’s friendship, now entered into a secret pact with him. Caesar’s master stroke was to persuade Crassus to join the partnership, the so-called first triumvirate. Crassus—like Pompey, a former lieutenant of Sulla—had been one of the most active of Pompey’s obstructors so far. Only Caesar, on good terms with both, was in a position to reconcile them. Early in 59 bce, Pompey sealed his alliance with Caesar by marrying Caesar’s only child, Julia. Caesar married Calpurnia, daughter of Lucius Piso, who became consul in 58 bce.

As consul, Caesar introduced a bill for the allotment of Roman public lands in Italy, on which the first charge was to be a provision for Pompey’s soldiers. The bill was vetoed by three tribunes of the plebs, and Caesar’s colleague Bibulus announced his intention of preventing the transaction of public business by watching the skies for portents whenever the public assembly was convened. Caesar then cowed the opposition by employing some of Pompey’s veterans to make a riot, and the distribution was carried out. Pompey’s settlement of the East was ratified en bloc by an act negotiated by an agent of Caesar, the tribune of the plebs Publius Vatinius. Caesar himself initiated a noncontroversial and much-needed act for punishing misconduct by governors of provinces.

Another act negotiated by Vatinius gave Caesar Cisalpine Gaul (between the Alps, the Apennines, and the Adriatic) and Illyricum. His tenure was to last until February 28, 54 bce. When the governor-designate of Transalpine Gaul suddenly died, this province, also, was assigned to Caesar at Pompey’s instance. Cisalpine Gaul gave Caesar a military recruiting ground; Transalpine Gaul gave him a springboard for conquests beyond Rome’s northwest frontier.

Between 58 and 50 bce, Caesar conquered the rest of Gaul up to the left bank of the Rhine and subjugated it so effectively that it remained passive under Roman rule throughout the Roman civil wars between 49 and 31 bce. This achievement was all the more amazing in light of the fact that the Romans did not possess any great superiority in military equipment over the north European barbarians. Indeed, the Gallic cavalry was probably superior to the Roman, horseman for horseman. Rome’s military superiority lay in its mastery of strategy, tactics, discipline, and military engineering. In Gaul, Rome also had the advantage of being able to deal separately with dozens of relatively small, independent, and uncooperative states. Caesar conquered these piecemeal, and the concerted attempt made by a number of them in 52 bce to shake off the Roman yoke came too late.

Great though this achievement was, its relative importance in Caesar’s career and in Roman history has been overestimated in Western tradition (as have his brief raids on Britain). In Caesar’s mind his conquest of Gaul was probably carried out only as a means to his ultimate end. He was acquiring the military manpower, the plunder, and the prestige that he needed to secure a free hand for the prosecution of the task of reorganizing the Roman state and the rest of the Greco-Roman world. This final achievement of Caesar’s looms much larger than his conquest of Gaul, when it is viewed in the wider setting of world history and not just in the narrower setting of the Greco-Roman civilization’s present daughter civilization in the West.

In 58 bce Rome’s northwestern frontier, established in 125 bce, ran from the Alps down the left bank of the upper Rhône River to the Pyrenees, skirting the southeastern foot of the Cévennes and including the upper basin of the Garonne River without reaching the Gallic shore of the Atlantic. In 58 bce Caesar intervened beyond this line, first to drive back the Helvetii, who had been migrating westward from their home in what is now central Switzerland. He then crushed Ariovistus, a German soldier of fortune from beyond the Rhine. In 57 bce Caesar subdued the distant and warlike Belgic group of Gallic peoples in the north, while his lieutenant Publius Licinius Crassus subdued what are now the regions of Normandy and Brittany.

In 56 bce the Veneti, in what is now southern Brittany, started a revolt in the northwest that was supported by the still unconquered Morini on the Gallic coast of the Strait of Dover and the Menapii along the south bank of the lower Rhine. Caesar reconquered the Veneti with some difficulty and treated them barbarously. He could not finish off the conquest of the Morini and Menapii before the end of the campaigning season of 56 bce; and in the winter of 56–55 bce the Menapii were temporarily expelled from their home by two immigrant German peoples, the Usipetes and Tencteri. These peoples were exterminated by Caesar in 55 bce. In the same year he bridged the Rhine just below Koblenz to raid Germany on the other side of the river, and then crossed the Channel to raid Britain. In 54 bce he raided Britain again and subdued a serious revolt in northeastern Gaul. In 53 bce he subdued further revolts in Gaul and bridged the Rhine again for a second raid.

The crisis of Caesar’s Gallic war came in 52 bce. The peoples of central Gaul found a national leader in the Arvernian Vercingetorix. They planned to cut off the Roman forces from Caesar, who had been wintering on the other side of the Alps. They even attempted to invade the western end of the old Roman province of Gallia Transalpina. Vercingetorix wanted to avoid pitched battles and sieges and to defeat the Romans by cutting off their supplies—partly by cavalry operations and partly by “scorched earth”—but he could not persuade his countrymen to adopt this painful policy wholeheartedly.

The Bituriges insisted on standing siege in their town Avaricum (Bourges), and Vercingetorix was unable to save it from being taken by storm within one month. Caesar then besieged Vercingetorix in Gergovia near modern Clermont-Ferrand. A Roman attempt to storm Gergovia was repulsed and resulted in heavy Roman losses—the first outright defeat that Caesar had suffered in Gaul. Caesar then defeated an attack on the Roman army on the march and was thus able to besiege Vercingetorix in Alesia, to the northwest of Dijon. Alesia, like Gergovia, was a position of great natural strength, and a large Gallic army came to relieve it; but this army was repulsed and dispersed by Caesar, and Vercingetorix then capitulated.

During the winter of 52–51 bce and the campaigning season of 51 bce, Caesar crushed a number of sporadic further revolts. The most determined of these rebels were the Bellovaci, between the Rivers Seine and Somme, around Beauvais. Another rebel force stood siege in the south in the natural fortress of Uxellodunum (perhaps the Puy d’Issolu on the Dordogne) until its water supply gave out. Caesar had the survivors’ hands cut off. He spent the year 50 bce in organizing the newly conquered territory. After that, he was ready to settle his accounts with his opponents at home.