In 48 BCE son of King Pontius Mithridates VI – Pharnaces II after defeating the governor of the Roman province – Asia – Domitius (Gnaeus Domitius Calvinus) in the battle of Nicopolis, attacked part of Roman territory and sold him into captivity its inhabitants. The king’s army also committed many atrocities on the Roman population and prisoners.
Caesar, having won the Alexandrian War, became interested in the events on the eastern borders of the empire. After spending the winter at the turn of 48/47 BCE he travelled from Egypt to Syria, where he handed over the management of the province to a friend and relative of Sextus Julius Caesar. He himself then sailed with the fleet from Egypt to Cilicia and marched to Cappadocia. During the march, Caesar met Dejotarus, the provincial governor of Galatia, who begged his forgiveness (he took part in the Battle of Pharsalos on Pompey’s side). Caesar ordered him to send all his cavalry to support the Roman army. Upon hearing that Caesar was approaching him, Pharnaces II immediately sent messengers with a proposal for peace, which Caesar immediately rejected. The Senate, despite its hatred of Caesar, fully supported his actions regarding the Pontic king.
The following year there was Caesar’s Roman campaign against Pharnaces. Initially, both sides conducted only diplomatic talks. The King of Pontus delayed the clash because he believed that Caesar would be forced to deal with the rest of Pompey the Great’s soldiers in North Africa and, unable to wait any longer, would eventually leave Asia. Caesar saw through his plan, but his army was too small and he had to wait for reinforcements.
Caesar had only 1,000 veterans (2 cohorts) from the 6th Legion, the Pontic (XXII) legion and separate troops (vexillationes) from the XXXVI legion and had to wait for the legion that the tetrarch of Galatia had promised him to deliver – Deiotarus. In addition, there was a small cavalry contingent in his army. Caesar’s army could count about 5,000,000 reinforcements, most of them battle-hardened and faithful soldiers.
Pharnaces II had an army of approximately 20,000 made up mostly of raised and tribal infantry. However, the king also had professional soldiers and cavalry.
The Pontic king decided to block Caesar’s troops near a small fortified town on a hill – Zela (today’s Tokat province in northern Turkey). Zela provided access to the most important passage through the mountain belt towards Pontus. These areas were extremely mountainous and crisscrossed by valleys. The Pontic army was located near the hill at Zela, when Caesar’s legionaries were fortifying the camp on another hill. On May 21, 47 BCE the promised army of Dejotarus came to Caesar, who immediately gave the order to launch the attack. Pharnaces, however, was faster and came Caesar from the steep side of the hill where the fortifications had not yet been completed. The idea of going up a steep slope seemed crazy, but the courage of the young king’s soldiers managed to overcome this obstacle. After a fierce fight, the 6th legion, commanded by Caesar, decided the fate of the battle. The Roman commander ordered a counter-offensive that pushed the Pontic forces down the hill and turned the enemy’s tight ranks into complete disarray. The king and a group of henchmen fled the battlefield, and the rest of the army either fled, captured, or died.
In the end, Caesar had a major victory at Zela, and the entire campaign lasted only 5 days. Caesar summed up this war in a letter sent to the Senate with three famous words: veni, vidi, vici (“I came, I saw, I conquered”). These words were to emphasize the speed and the fullness of the Roman victory. A letter with these words was delivered to Senator Amincius. The defeated Pharnaces fled to Crimea, where he died the same year in the fight against the local usurper (a former subordinate).
The description of the battle at Zela survived thanks to the anonymous author of the book “On the Alexandrian war”. This work is sometimes ascribed to Caesar himself.