Caesar’s conquest and pacification of Gaul was approaching completion by 56 B.C.E. Most of the country had come to heel and was now a Roman province, except for sporadic outbreaks of fierce resistance. In his Commentarii de Bello Gallico, Caesar described how the ferocious Helvetii, having left their territory of what is now Switzerland, had migrated into Gaul, intending to get as far as the English Channel and resettle there. Caesar’s armies attacked them in their migration, and in Annecy, on the river Arroux, he wiped them out by the tens, perhaps hundreds, of thousands, turning the survivors back toward Switzerland. The same infiltration into Gaul, followed by the same costly expulsion, was attempted by German tribes. North of the Seine were the so-called Belgae, a warlike people consisting mainly of Germans intermarried with Celts. They were extremely suspicious of Caesar, and should have been. When Caesar established his winter headquarters on Gallic territory, and gave every sign of meaning to stay, they mobilized a full 300,000 warriors. Caesar’s reply was to raise two more legions in Cisalpine Gaul, bringing his total force to eight.
The coherence of the Belgic armies now began to disintegrate, largely because of supply shortages. Only the tribe known as the Nervii could keep an army in the field, and Caesar annihilated them in a battle on the Sambre in 57 B.C.E. Thus the resistance in Gaul only lasted for two military seasons. In the end, fully a third of all Gauls of military age were killed, and another third were sold into slavery: a toll which all but destroyed the masculine population of the province, made it incapable of further resistance, and made Caesar even more colossally rich than before. The Gallic leader Vercingetorix, a brilliant, charismatic figure who had given Caesar the most difficult and stubborn resistance of his career, was besieged and finally captured at Alesia in 52 B.C.E. Brought back to Rome in chains, he was paraded in Caesar’s triumph and then ignominiously strangled in a dungeon.
By 52 B.C.E., little opposition to Rome was left; by 50, there was none. The conquest of Gaul changed Rome from a Mediterranean power to a pan-European one, since (in the words of the historian Michael Grant) “a vast conglomeration of territories in continental and northern Europe had now been opened up to Romanization.” It also radically changed Gaul, transforming it, in effect, into an embryonic form of France. It was opened, though at great cost in blood and suffering, to classical culture.
With long-term thoughts of enlarging Rome’s imperium still further, Caesar dispatched an expedition across the Rhine to Germany in 55 B.C.E., with inconclusive results; this was less an invasion than a probe. Its purpose was to show Roman power to the Germans on German territory, which would deter them from crossing into Gaul. A friendly, or at least complaisant, German tribe called the Ubii offered him boats in which his troops could cross the Rhine, but Caesar refused—it would not look good to depend on the Germans to get him into Germany. Instead, by engineering means that are not clear from his own account, his men built a timber bridge across the mighty river. His army spent three weeks or so marauding and burning villages on the German side, and then withdrew, having made its point, and demolished its bridge behind it.
Next came an expedition to Britain. Why Caesar wanted to invade the island, which had never been attacked by Rome before, is unclear. Perhaps he suspected that the Britons would join with the Gauls in some later counterattack; perhaps he was lured by exaggerated stories of fabulous wealth (gold, silver, iron, and pearls) to be looted there. Or perhaps he merely wanted intelligence about this unknown place, and nobody could supply it to him. Whatever the motive, in 55 he led a fleet of transports and men-of-war directly to the southeastern coast of Britain, where they met with vilely contrary weather and stiff resistance from the “barbarian” infantry and cavalry. The Romans eventually succeeded in landing (at the present site of Deal) and making the Britons sue for peace, but they did not penetrate far inland, it was a shallow victory at best, and they brought back little information and less booty.
Caesar tried again the next year, 54. He assembled a new fleet of some eight hundred vessels, carrying five legions and two thousand cavalry. This time the conditions were more favorable, and the Romans fought their way north, crossing the Thames with intent to attack the British commander Cassivelaunus. They besieged this king’s stronghold in Hertfordshire, and captured him; terms were made. But then news arrived that an insurrection was brewing among the Gauls, so, with reluctance, Caesar withdrew his army across the Channel; the complete conquest of Britain, and its reduction to a province of Rome, would have to wait for nearly a century, until it was achieved by the armies of the Emperor Claudius.
But precisely because so little was known about Britain in Rome, the very fact of going there endowed Caesar with mystique and celebrity at home, on top of the glory he had earned with his conquest of Gaul and the readership his brilliant Commentaries, the best book on war a Roman had ever written, had acquired. He was, moreover, extremely wealthy now from the sale of Gallic prisoners-of-war as slaves. He raised the scale of his influence-buying. One of the consuls of the year 50 B.C.E., Lucius Aemilius Paullus, is said to have raked in 36 million sesterces from Caesar—this at a time when a line soldier in the Roman army was paid a thousand sesterces a year. Surpassingly rich, overwhelmingly popular: nothing could have been more propitious for a major political career in Rome.
The big problem was that he could not return to Rome. He could not come back with his legions, because by law no commander could enter the city with his troops. But he could not come back without them, for that would have meant laying down his command and exposing himself to prosecution by his many enemies.
But he had been moving south. In January 49, the Senate sent him orders to disband his army. Caesar received them on the northern side of a small river called the Rubicon, the boundary between Cisalpine Gaul and Italy proper. (The name, deriving from the Latin ruber, red, referred to the color of its clay-filled water.) Caesar’s reaction to this letter was prompt and decisive. “As for myself,” he declared in his Civil War (1.9), “I have always reckoned the dignity of the Republic of first importance and preferable to life. I was indignant that a benefit conferred on me by the Roman people was being insolently wrested from me by my enemies.” And so, in that legendary phrase which has come to mean taking any fateful and irrevocable decision, he crossed the Rubicon and entered Italy with his troops.
This inevitably meant civil war. The commander of Rome’s troops in the war was Gnaeus Pompeius Magnus (106–48 B.C.E.), known to history as Pompey, a resourceful and highly skilled commander, the only man in Rome capable of standing up against Julius Caesar. Pompey’s career, up to this point, had been marked by brilliant successes which also served dramatically to highlight the weaknesses of the aging republican system. From now on, Roman politics would have less and less to do with democracy, becoming more and more determined by ambitious individuals backed by their own armies.
Quite early in his career, Pompey showed every sign of developing into just such a prototypical strongman, utterly ruthless and bent on power. Sulla had recognized that Rome’s growing empire could not possibly be governed by popular acclamation, by democratic votes. That system was too unwieldy. His policy, therefore, was to shift the authority of the state away from Rome’s tribunes, magistrates and popular assembly, which he regarded as mere rabble, and return them to the Senate. Under Sulla’s new system, the senators got all their judicial powers back, while consuls and praetors, shorn of their military power, had to content themselves with being the Senate’s good servants. But there was a question: what if some new Roman warlord turned on the Senate with his forces and simply threw them out? Sulla’s solution was to pass a law whereby there would be no Roman armed force in Rome. As soon as any returning soldiers, or their officers, crossed the limits of the urbs Romae, they would automatically have to lay down their arms, surrender their command, and become private citizens once more. Of course, this needed enforcement, which Sulla, the winner of the war against Mithridates, king of Pontus, was prompt to supply. He had accumulated huge reserves of booty and cash, and these financed his own invasion of Italy in 83 B.C.E. Naturally, this did not go without a hitch, for there were strong anti-Sulla feelings in both Sicily and North Africa, and Sulla enlisted the brilliant and ruthless young Pompey to suppress them—which he did with unrestrained butchery and bloodshed. By 81 B.C.E. the anti-Sulla factions were crushed, and Pompey—who was only twenty-five at the time—was in a position to demand a full triumph from Sulla on his return to Rome, and the cognomen Magnus, “Pompey the Great,” attached to his name. There was no denying that Pompey had burst through the exclusive ranks of Rome’s upper establishment, the optimates. No previous Roman had won such an honor so early in his military career.