In 49 BC, civil war had broken out in Rome. Once friends, Ivlivs Caesar and Pompeivs Magnus now were fighting for power in a conflict that threatened to destroy the Republic. While the Romans were distracted with this conflict, Pharnakes II of Pontus took advantage of the situation to claim the lands of his father Mithridates VI. In a swift campaign he made himself the ruler of Colchis and Lesser Armenia. Deiotarus, the Galatian king of Lesser Armenia appealed to Domitius Calvinus, the Roman officer of Caesar in Asia, for help against this menace. The Romans first met Pharnakes at Nicopolis in Anatolia. Using trenches to protect his flanks and superior cavalry, Pharnakes defeated Calvinus. Great surprise and fear spread across the region when the Romans were defeated by the Pontic army giving Pharnakes the chance to overwhelm all of Pontus.
After the news of the Roman defeat spread further, Caesar had to take actions against this enemy of Rome. He went by himself to solve the conflict with Pharnakes for once and for all. Caesar sailed from Egypt with a small army along the coast of Syria and through Cilicia to Pontus. On the way he collected more troops, but of all the soldiers he got, only one thousand were not raw levies. With this army he went to subdue the son of Mithridates.
Zela is a fortified town in Pontus. All around are a great number of large mountains, intersected by valleys. The highest of these, which is celebrated for the victory of Mithridates, the defeat of Triarius, and the destruction of a Roman army during the Mithridatic Wars, is almost three miles from Zela, and has a ridge that extends close to the town. On this hill Pharnakes camped, with all his forces, repairing the fortifications of a position which had proved so fortunate to his father.
The next morning, Pharnakes arranged all his troops in the order of battle before his camp. Caesar, on account of the disadvantage of the ground, believed that the king was reviewing them according to military discipline, or was intending to slow down his works, by keeping a great number of his men under arms. Caesar, not knowing what was in the mind of Pharnkaes, kept only his first line in order of battle while he commanded the rest of the army to go on with their works.
Sure of himself and anxious, Pharnakes ordered the attack. He felt that the fortune of his father would turn things in his favor.
Caesar at first couldn’t believe that the attack was intended as an assault. He considers it a mere threat to interrupt his entrenching, and made his common mistake of only ordering out his first line to secure. The Romans were not prepared for the clash and were really surprised when they saw the enemy charging uphill.
The scythed chariots of Pharnakes opened the action, but their advance was partially stopped by the darts from the Roman army. The Pontic infantry soon closed in. The impact to the Roman line was severe, but the Sixth legion on the Roman right flank stood firmly. The chariots had broken through the center of the line and the Pontic infantry soon followed through the gap. The danger to the Roman line was huge and Caesar had to fill the gaps with reserves while also taking care of what was happening on the left flank.
After a long battle, the one thousand men of the Sixth legion prevailed over all odds and these brave men led the rest of the line with their great example of courage. Fortune did not desert Caesar and Pharnakes could no longer maintain the energy and his army could not stand its ground driven downhill with great slaughter.
In this battle, taking great risk and showcasing splendid courage, Caesar snatched a victory and settled the Pontus problem in just four days. Caesar himself, in a letter to a friend in Rome, famously said the phrase: “Veni, vidi, vici” (“I came, I saw, I conquered”).
Pharnakes had to retreat quickly back to the Bosporus, where he managed to assemble a small force of Scythians and Sarmatians. However his plans for a new campaign ended when a former governor of his, Asandar, attacked his new army and killed him.