The battle of the Nile (February 47 BC) was the final action of Caesar’s Alexandrian War, and saw him unite with the relief army under Mithridates of Pergamum to defeat the army of Ptolemy XIII. (Great Roman Civil War)
In the aftermath of his victory at Pharsalus (48 BC), Caesar pursuing the fleeing Pompey across the eastern Mediterranean. Eventually Pompey reached Egypt, where he was murdered by agents of the young Pharaoh Ptolemy XIII. Caesar arrived a few days later, and was soon dragged into Egyptian politics. He had followed Pompey with two under strength legions, and soon found himself outnumbered and besieged in Alexandria by an army that fought for Ptolemy and his younger sister Arsinoe. Caesar sided with Ptolemy’s sister Cleopatra, although his main aim during the siege was survival.
Soon after his arrival in Egypt, Caesar sent out messages ordering his allies to send reinforcements to Egypt. King Mithridates of Pergamum, one of his trusted allies, was sent to raise forces in Syria and Cilicia. After raising his army, he marched it south towards Egypt. Achillas, the first commander of the Alexandrian army, put a garrison in Pelusium, a strong fortress on the north-eastern frontier of Egypt. Mithridates brushed this garrison aside in a single day, and resumed his advance across Egypt.
By now Ptolemy XII had taken command of the Alexandrian army, replacing his sister Arsinoe, who had herself replaced and killed Achillas. He sent a large force to try and block Mithridates’s progress. Mithridates had adopted Roman military customs, and had built a fortified camp on the eastern side of one of the branches of the Nile. Ptolemy’s troops crossed the river in several groups. The first group across attacked this camp, but without success. When it became clear that the Alexandrians were disorganised, Mithridates attacked and routed them. The survivors re-crossed the Nile and prepared for a second attack.
News of this first battle soon reached Caesar and Ptolemy. Both men decided to leave Alexandria to take part in the upcoming battle in the Delta. Ptolemy was able to use the branches of the Nile to reach the camp of his defeated troops, while Caesar sailed along the coast. Although Ptolemy had the easier route, Caesar was able to arrive in time to prevent him from attacking Mithridates while he was still isolated.
Once Caesar had joined Mithridates, he advanced towards Ptolemy’s camp. This was on the far side of a branch of the Nile, and Ptolemy sent his cavalry and some of his light infantry to defend the line of this river. For some time they were able to stop Caesar, but eventually some of his German cavalry managed to swim the river, while the legionaries built a simple bridge using some tall trees. The Alexandrians attempted to escape to Ptolemy’s camp, but most were killed during the pursuit.
Caesar pursued closely, hoping that his arrival would convince the Alexandrians to surrender or flee. Instead he found them in a secure position in a strongly fortified camp, and decided not to risk an immediate attack.
The main Egyptian camp was built on a hill close to the Nile. It was linked to a nearby fortified village by a line of communications. The Alexandrians also had a fleet on the Nile. On the following day Caesar decided to attack that village with his entire army, in the hope that he would be able to follow its retreating garrison into the main camp. The village fell as planned, but the second part of the plan failed, and Caesar’s men came to a halt at some distance from Ptolemy’s camp. He then attempted to attack on two side - from the plains and along the gap between the camp and the Nile, but both attacks failed. However during this fighting most of the Alexandrians moved to the parts of the camp that were under attack, leaving the tallest part of the hill undefended. Caesar sent a small force under Carfulenus to attack this part of the camp, and they were soon able to overwhelm the few defenders who had been left there. Once the Romans had broken into the camp in one place, its defenders became demoralised, allowing the Romans to break in at several other places. The Alexandrians attempted to flee, but many were crushed in the ditch that surrounded the camp, while others were drowned in the Nile. Amongst the dead was Ptolemy, who had reached the apparent safety of one of his ships, but drowned when that ship was swamped by a crowd of refugees.
In the aftermath of this victory, Caesar returned to Alexandria, where the remaining Egyptian troops surrendered. He placed Cleopatra on the throne, alongside her younger brother, Ptolemy XIV. After remaining in Egypt for a few months, Caesar then returned to the Roman world to resume the Great Roman Civil War.