Battle of Dyrrhachium (48 BC)

By the end of Julius Caesar's first year as consul he had accumulated a large list of lawsuits. Roman law gave government officials immunity from prosecution but only during their term of office. Once he became a private citizen Caesar knew he would be vulnerable.

Instead, as was usual for a consul at the end of his term, Caesar obtained a proconsul position, or governorship, over the territories of Cisalpine Gaul and Illyricum (modern day Albania), with the later addition of Transalpine Gaul. What was unusual was the length of Caesar's term as proconsul, which was for five years instead of the usual one year. Moreover, prior to the end of his five years as proconsul of Gaul and Illyricum, Caesar assisted his allies Crassus and Pompey in being elected consuls, who in turn extended his pro-consulship for a further five years.

At the end of his term as proconsul, having now met the condition that there be a minimum of ten years between elections as consul, Caesar intended to stand for the consulship in absentia, and upon being elected go straight from his proconsular command into the second consulship. In this way, he would maintain his imperium and thereby not be vulnerable to lawsuits.

However, the Senate ordered him to resign command of his army. Caesar replied that he would agree to resign his military command only if Pompey followed suit. Offended by Caesar's response, the Senate demanded he immediately disband his army, or be declared an enemy of the people. In 50 BC, at his Proconsular term's expiry, the Senate forbade Caesar's standing for election in absentia for a second consulship and because of this, Caesar thought he would be prosecuted and rendered politically marginalised if he entered Rome without consular immunity or his army. Caesar responded by marching on Rome and he forced the unprepared Pompey and his allies to flee to Greece, starting the Great Roman Civil War.

Caesar did not immediately give chase to Pompey and instead consolidated power in Rome and Italy. He had other problems as well; Pompey had left him with no ships to cross the Adriatic, and Spain had begun to mobilize against Caesar. After gathering the remainder of his forces from Transalpine Gaul (modern day France) he marched into Spain and subdued enough of the country so that it wouldn't intervene during his campaign against Pompey. He then turned his full attention to Pompey.

Having only assembled half the needed ships, Caesar decided to take seven available legions across the Adriatic, and to then have the ships travel back to Brundisium, (modern-day Brindisi), and transport the remaining legions once they had arrived at Brundisium. Travel across the Adriatic Sea to Greece would ordinarily be tricky, but was made more so given that it was winter. However, this situation did assist Caesar because the Adriatic was sufficiently treacherous to deter the war galleys of Pompey's fleet, commanded by Caesar's former co-consul Marcus Calpurnius Bibulus, at Corfu. As it was winter Bibulus was unprepared and Caesar was able to sail through the blockade easily and form a beachhead at Epirus with the first half of his army. Bibulus, however, was able to block Caesar's attempt to sail his reinforcements stuck at Brundisium. Bibulus died while conducting this blockade and no overall naval commander was appointed by Pompey. At some point Lucius Scribonius Libo attempted to make the blockade more secure by seizing the island off Brundisium preventing Caesar's reinforcements from sailing anywhere. However, Libo could not sustain this position because of a lack of water.[3]

Caesar's blunder had put him in the worst possible position any army could find itself. His army had no way to resupply from Rome due to the naval blockade, he couldn't resupply locally as Greece was pro-Pompey and closed their gates to Caesar, and his army was only at half strength. So dire was his situation that he made several attempts to discuss peace with Pompey but was refused at every channel. Realizing he was going to have to fight his way out, he attempted another winter blockade run back to Italy to lead his remaining forces to Greece. His luck was not with him and the rough seas and storms forced him back. However, his Master of the Horse Marc Antony fired up his troops and after several attempts evaded Libo's blockade and managed to land at Nympheum (Shëngjin in Albania) with four more legions. It was now a race against time as both Caesar and Pompey rushed to meet Antony. Although Pompey reached Antony first Caesar was right on his heels and Pompey prudently moved his forces to Dyrrachium to prevent becoming caught between the two forces.

At Dyrrachium Pompey held a strong defensive position; his back was guarded by the sea, and at his front there were hills that commanded the immediate area. He established his camp on the top of a rocky outcrop called Petra, overlooking the Egnatian Way and protecting a reasonable anchorage for his ships about five miles to the south of his base.[4] An assault on Pompey's position was nearly impossible, therefore Caesar ordered men to build earthworks and fortifications to pin Pompey against the sea. His motives for doing so were three-fold: to prevent Pompey from getting fodder for his animals; to render his cavalry ineffective and thus protect his own foraging parties; and to reduce Pompey's standing in the eyes of the foreigners and his own men by putting him on the defensive and making him openly refuse battle.[5] Pompey responded with earthworks and fortifications of his own; thereby enclosing an area of grazing land as wide as possible and trying to stretch Caesar's lines to its limits.[6]

Between these two fortifications a no man's land was created which saw constant skirmishes with little or no gain. Caesar records one battle in particular, fought in mid-June, for the control of the vital hill of Paliama, some three miles south of Pompey's camp.[7] Using archers, slingers and lightly armed infantry supported by catapults, Pompey's men dislodged the Caesarian Ninth Legion from its position, but failed to take full advantage of the withdrawal and their pursuit was halted by an uphill counter-charge by Caesar's legionaries.[7]

Caesar held the outlying farmland but it had been picked clean and Pompey, with the sea at his back, was able to be resupplied by ship. However, as the siege wore on, their positions began to change. Pompey found it difficult with the limited land he controlled to create enough fodder for his horses, and other supplies such as fresh water became more and more difficult to maintain. The autumn harvest was approaching and soon Caesar would have enough food to prolong his position. If Pompey's army was not to be destroyed by disease during the summer and lose all its animals, Caesar's siege-works had to be breached. Pompey decided to try and lure Caesar away from the fortifications by means of a false message that some of the inhabitants of Dyrrachium were prepared to betray the town to him, and meanwhile lauch a three-pronged attack against forts in the centre of the siege-line. At two of these forts one cohort under Lucius Minucius Basilus and three cohorts under Gaius Volcatius Tullus put up stiff resistance against five of Pompey's legions until they were relieved by a force of two legions from the main camp under Publius Cornelius Sulla. The Pompeians became cut off on a hill-top between the two lines for five days before Pompey could withdraw them. Caesar reckoned the Pompeian losses at 2,000.[8]

At Dyrrachium Caesar only just escaped the ambush Pompey had set for him. He responded by building fortifications to cut off the two approaches to the town and prevented Pompey's horses from grazing in the countryside to the north.[9]

By midsummer, though, Pompey had a fortunate stroke of luck. Two Gallic noblemen were caught stealing the pay from auxiliary cavalry under their command, but managed to escape to Pompey. With these two men on his side, Pompey was able to discover the weakest point in Caesar's wall.[10] At the southern end of the circumvallation, where it came close to the sea, Caesar was building a second wall 200 metres south of the main one to protect his defenders from a sea-borne attack from the rear, but it was unfinished and the area between the walls was undefended from the seaward side.[11]

Pompey mounted a frontal attack of six legions against Caesar's line where it joined the sea and where the IX legion was stationed. Pompey also sent some auxiliaries and light infantry to attack by sea. Heavily outnumbering the Caesarian troops and attacking them from the front and the rear, the Pompeian troops broke through the weakened fortifications, causing the Ninth to pull back from the onslaught with heavy losses. Caesar swiftly reinforced the breach with 4,000 men. Twelve cohorts under Mark Antony then counterattacked, re-securing part of the wall and pushing Pompey's disordered forces back. Although Caesar's counterattack was initially successful, Pompey's forces were simply too numerous. During the morning Pompey consolidated his newly-won position by building a camp south of the Caesarian walls and put five of his legions there, he then sent the sixth to occupy a small camp between the walls that had been abandoned by Caesar, and enlarged the defences. Caesar responded by sending 33 cohorts to attack this position. Although the attack was initially successful, the Caesarian troops were outnumbered 2:1 and Pompey's troops fought hard. Pompey sent a large force of infantry and 3,000 cavalry to outflank Caesar's right wing. Caesar first ordered his troops on the right to stand firm, but then saw the danger of being outflanked. He ordered a retreat which soon became a panicked and disordered rout. The counterattack on Pompey's camp disintegrated completely. At first Caesar personally tried to stem the retreat, but the fleeing troops did not stop until they reached their own camps. Pompey refrained from pursuing Caesar's routed forces and this allowed them to regroup. Caesar gives his own losses at about 1,000; Pompey's were presumably less. After the failure of the counterattack and considering the losses incurred, Caesar resolved to give up attempting to besiege Pompey and to change the entire strategy of the campaign.[12]

Pompey ordered a halt, believing that Caesar had been decisively beaten, and also suspecting a trap. Caesar's men regrouped in their camp and Caesar made preparations for a strategic withdraw. According to Plutarch, Caesar remarked on that decision saying, "Today the victory had been the enemy's, had there been any one among them to gain it."[13]

Caesar, by various stratagems, managed to retreat south with the remainder of his army and avoided being caught by the pursuing cavalry of Pompey. He sent some of his cohorts to reinforce the garrisons of Apollonia and Oricum, and propelled the bulk of his remaining troops into Thessaly. The Caesarian general Gnaeus Domitius Calvinus and the Pompeian general Scipio Nasica were both in that country with their respective armies, and both Caesar and Pompey then aimed to link up with their corresponding forces. Upon entering Thessaly, Caesar captured the town of Gomphi and regrouped with Domitius, allowing his men to resupply, rest and then move towards Pharsalus. Pompey linked up with Scipio and then with a force which now numbers nine-and-a-half legions, 7,000 cavalry and numerous light-armed auxiliaries he also reached Pharsalus. Both armies now prepared for the decisive battle which was fought four days later on 9 August 48 BC.[14]

• Livius.org: Dyrrhachium (48 BC)