In the spring of 58 B.C. alarming intelligence from beyond the Alps caused Cæsar to hasten from Rome into Transalpine Gaul. Now began a series of eight brilliant campaigns directed against the various tribes of Gaul, Germany, and Britain. In his Commentaries Cæsar himself has left us a faithful and graphic account of all the memorable marches, battles, and sieges that filled the years between 58 and 50 B.C. The year 55 B.C. marked two great achievements. Early in the spring of this year Cæsar constructed a bridge across the Rhine, and led his legions against the Germans in their native woods and swamps. In the autumn of the same year he crossed, by means of hastily constructed ships, the channel that separates the mainland from Britain, and after maintaining a foothold upon that island for two weeks withdrew his legions into Gaul for the winter. The following season he made another invasion of Britain; but, after some encounters with the fierce barbarians, recrossed to the mainland without having established any permanent garrisons in the island. Almost one hundred years passed away before the natives of Britain were again molested by the Romans (see p. 311).

In the year 52 B.C., while Cæsar was absent in Italy, a general revolt occurred among the Gallic tribes. It was a last desperate struggle for the recovery of their lost independence. Vercingetorix, chief of the Arverni, was the leader of the insurrection. For a time it seemed as though the Romans would be driven from the country. But Cæsar's despatch and military genius saved the province to the republic.

In his campaigns in Gaul, Cæsar had subjugated three hundred tribes, captured eight hundred cities, and slain a million of barbarians—one third of the entire population of the country. Another third he had taken prisoners. Great enthusiasm was aroused at Rome by these victories. "Let the Alps now sink," exclaimed Cicero: "the gods raised them to shelter Italy from the barbarians: they are now no longer needed."

RESULTS OF THE GALLIC WARS.—The most important result of the Gallic wars of Cæsar was the Romanizing of Gaul. The country was opened to Roman traders and settlers, who carried with them the language, customs, and arts of Italy.

Another result of the conquest was the checking of the migratory movements of the German tribes, which gave Græco-Roman civilization time to become thoroughly rooted, not only in Gaul, but also in Spain and other lands.

RIVALRY BETWEEN CÆSAR AND POMPEY: CÆSAR CROSSES THE RUBICON.—While Cæsar was in the midst of his Transalpine wars, Crassus was leading an army against the Parthians, hoping to rival there the brilliant conquests of Cæsar in Gaul. But his army was almost annihilated by the Parthian cavalry, and he himself was slain (54 B.C.). His captors, so it is said, poured molten gold down his throat, that he might be sated with the metal which he had so coveted during life. In the death of Crassus, Cæsar lost his stanchest friend, one who had never failed him, and whose wealth had been freely used for his advancement.

The world now belonged to Cæsar and Pompey. That the insatiable ambition of these two rivals should sooner or later bring them into collision was inevitable. Their alliance in the triumvirate was simply one of selfish convenience, not of friendship. While Cæsar was carrying on his campaigns in Gaul, Pompey was at Rome watching jealously the growing reputation of his great rival. He strove, by a princely liberality, to win the affections of the common people. On the Field of Mars he erected an immense theatre with seats for forty thousand spectators. He gave magnificent games, and set public tables; and when the interest of the people in the sports of the Circus flagged, he entertained them with gladiatorial combats. In a similar manner Cæsar strengthened himself with the people for the struggle which he plainly foresaw. He sought in every way to ingratiate himself with the Gauls; increased the pay of his soldiers; conferred the privileges of Roman citizenship upon the inhabitants of different cities in his province; and sent to Rome enormous sums of gold to be expended in the erection of temples, theatres, and other public structures, and in the celebration of games and shows that should rival in magnificence those given by Pompey.

The terrible condition of affairs at the capital favored the ambition of Pompey. So selfish and corrupt were the members of the Senate, so dead to all virtue and to every sentiment of patriotism were the people, that even such patriots as Cato and Cicero saw no hope for the maintenance of the republic. The former favored the appointment of Pompey as sole consul for one year, which was about the same thing as making him dictator. "It is better," said Cato, "to choose a master than to wait for the tyrant whom anarchy will impose upon us." The "tyrant" in his and everybody's mind was Cæsar.

Pompey now broke with Cæsar, and attached himself again to the old aristocratic party, which he had deserted for the alliance and promises of the triumvirate. The death at this time of his wife Julia, the daughter of Cæsar, severed the bonds of relationship at the same moment that those of ostensible friendship were broken.

The Senate, hostile to Cæsar, now issued a decree that he should resign his office, and disband his Gallic legions by a stated day. The crisis had now come. Cæsar ordered his legions to hasten from Gaul into Italy. Without waiting for their arrival, at the head of a small body of veterans that he had with him at Ravenna, he crossed the Rubicon, a little stream that marked the boundary of his province. This was a declaration of war. As he plunged into the river, he exclaimed, "The die is cast."