The First Triumvirate

While Caesar was in Rhodes, the third Mithridatic War broke out, and he served in it for a short time. He returned to Rome in the winter of 74–73 B.C., and found that he had been elected pontifex, or high priest, an important political position. Thereafter he steadily rose in rank and in popular favor.

In 60 B.C. Caesar formed a political alliance with Pompey, commander of the Roman armies, and the wealthy Marcus Licinius Crassus. This alliance, called the First Triumvirate, was a private understanding among the three by which they controlled Rome's most important offices.

Caesar became consul in 59 B.C., and the next year obtained for himself the military rule of Cisalpine and Transalpine Gaul (northern Italy and southern France) for five years. In 56 the triumvirs agreed that Crassus would have military charge of Syria, and Pompey of Spain. At the same time, Caesar's command of Gaul was extended to 49 B.C. Caesar's campaigns in Gaul brought the entire region (modern France and Belgium) under Roman control, established him as a great military leader, and won him the loyalty of his legions. Caesar invaded Britain twice (55 and 54 B.C.) but made no attempt to occupy the island.

Meanwhile, Crassus had been killed in the East in 53 B.C. Pompey, who had been made sole consul in 52, began to plot with the Senate to lessen Caesar's influence. In December, 50 B.C., the Senate commanded Caesar to send home part of his legions or be considered an outlaw. Caesar then led his legions across the Rubicon, the little stream that separated his province from Italy, and marched on Rome in January, 49 B.C. The Triumvirate had come to an end.