The Battle of Pharsalus, 9 August 48 BC

Pharsalus was one of the decisive battles of world history. It ended the 500-year history of the Roman Republic and launched the 500- year history of the Roman Empire. It ended the rule of the Senate and replaced it with the rule of the Emperors.

What was at stake was the outcome of the entire ‘Roman Revolution’, a century-long process of increasingly violent conflict which pitted the Optimates (‘the best men’) against the Populares (‘the populists’).

It was a struggle to decide whether the Roman state would remain dominated by an exclusive aristocracy of senators or be opened up to the homines novi (‘the new men’) – the officers, administrators, businessmen, and provincial gentry of a fast-expanding Empire.

This underlying social conflict shaped the battle. Pharsalus was a triumph of three immediate factors: centralised command and control; a superbly professional and experienced army; and Caesar’s tactical brilliance.

But these factors reflected deep-rooted differences between the Pompeian and Caesarian armies – differences rooted in the social conflict that was tearing the Roman Republic apart. Pharsalus was the defeat of an ancien régime of corrupt, snobbish, opportunist politicians by an army that embodied the spirit of the new age.

Pompey the Great

When Caesar’s governorship of Gaul came to an end, he sought a new consulship that would guarantee him immunity against prosecution by his enemies in Rome’s highly political law-courts. His enemies – who were many – were determined that he should return to Rome a private citizen, so that he could be stitched up and destroyed by legal action.

It was this that had caused him to cross the Rubicon into Italy at the head of his veteran Gallic War army – making him, in strict legal terms, an invader and an outlaw.

The Senate put its trust in Gnaeus Pompeius Magnus – Pompey the Great – Rome’s other great general. Roman politics in the Late Republic was dominated by a succession of great politician-generals, and the Senate could not hope to raise armies of sufficient strength to oppose Caesar without winning over the only other man in the state of comparable stature and influence.

Tens of thousands of Pompey’s veterans were settled on Italian farms. Tens of thousands of Greeks, Anatolians, and Syrians owed allegiance to him following his great campaigns of conquest in the eastern Mediterranean in the 60s BC. ‘I only have to stamp my foot,’ he proclaimed, ‘and all over Italy legionaries and cavalrymen will rise from the ground.’

Nonetheless, Pompey needed time, whereas Caesar had an army in being – eight legions, 40,000 men, plus auxiliaries, perhaps another 20,000 – and with these, displaying traditional celeritas (‘speed’), he swept south and captured Rome. Pompey, the majority of the Senate, and 25,000 soldiers fled across the Adriatic to Greece.

Dyrrhachium

Here, in his old bailiwick, Pompey called in favours and his army grew. When Caesar, after a whirlwind campaign in Spain, followed him in November 49 BC, Pompey’s army had swelled to perhaps 100,000 in total.

Caesar was taking enormous risks. He lacked sufficient shipping, so was compelled to divide his army and invade a hostile shore in two contingents, crossing the sea, moreover, in early winter. His own contingent of 25,000 arrived safely, but Mark Antony’s 20,000 men were blockaded at Brundisium on the Italian side.

When Antony finally arrived (in February 48 BC), Caesar besieged Pompey’s army at Dyrrhachium, on the coast of Epirus (today Albania), despite the latter’s still 2:1 advantage in numbers. But his siege lines – miles long – were stretched too thin, and on 20 May his defences were turned by Pompey’s massed assault, forcing him to retreat from the coast into the Greek interior.

Caesar’s boldness had led to disaster, for he was now cut off from his main base in Italy, and therefore from resupply and reinforcement, and he was having to live off the land in territory strongly Pompeian in sympathy. Starvation became a real danger.

Pompey – past his best, but still imbued with military wisdom – favoured a strategy of attrition: boxing Caesar in, harassing his foragers, denying him freedom of movement, but avoiding the risks of pitched battle against Caesar’s veterans.

Pompey’s army

Pompey’s forces were strategically strong, but tactically weak. He had numbers and he had popular support. But his army lacked experience and coherence. His legions were newly raised. The veterans who had answered his call and returned to the colours were relatively old, and they had not had time to train, discipline, and harden the fresh recruits who made up the bulk of the rank-and-file.

As for his Eastern allies, they were a hodge-podge of variable quality who could not readily be integrated into a coherent military force. The Greek historian Appian gives a strong sense of the unmanageably polyglot nature of much of Pompey’s vast host:

Apart from Greeks, there were contingents from nearly all the peoples as you go in a circle along the coast towards the east: Thracians, Hellespontines, Bithynians, Phrygians, and Ionians; Lydians, Pamphylians, Pisidians, and Paphlagonians; the people of Cilicia, Syria, and Phoenicia; the Jews and the neighbouring Arabs; Cypriots, Rhodians, Cretan slingers, and various other islanders.

He also mentions the various client kings – of Galatians, Cappadocians, Armenians, and others – who came with their contingents.

This was less an army than a pageant, a durbar, a display of political power. And it is notable that when the time for battle came, most of this host of Eastern allies were excluded from the main battle-line – where their infirmity could only have weakened it wherever they took station.

Nor was this the only problem. Pompey’s camp was full of senators, most of them men of little military experience, but many with the arrogance of blue-blooded aristocrats born to wealth and power.

What they saw was Pompey’s great numbers, Caesar’s relatively few, and an enemy in flight after defeat at Dyrrhachium. So Pompey found himself accused of cowardice, or premature old age, or a desire to cling to the trappings of power, when he refused battle. Pompey eventually succumbed to this pressure, and, against his better judgement, committed himself to the very battle that was Caesar’s only chance.

Pompey’s deployment

By early August 48 BC, the two armies were camped about four miles apart, near the town of Pharsalus in Thessaly, northern Greece. Each day, Caesar deployed his legions, offering battle, since, short of supplies and increasingly constrained by the numerical superiority of his enemies, he was eager for an opportunity to destroy Pompey’s army.

Pompey, however, would deploy on the lower spurs of the hill on which his camp was located, avoiding battle by keeping to strong defensive ground.

Then, on the very day Caesar had decided to move away, since he had exhausted the resources of the surrounding countryside, Pompey deployed on level ground, giving Caesar the opportunity to fight the battle he craved on equal terms. He cancelled his planned march and told his men: ‘Our spirits are ready for battle. We shall not easily find another chance.’

Before forming his battle- line, moreover, he ordered his men to level the rampart and backfill the ditch around their camp. This was an extraordinary gesture, a powerful assertion of moral dominance, since it meant the Caesarians would have no refuge in the event of defeat.

Pompey’s main battle-line – excluding the Eastern allies who were consigned to the fringes of the battlefield – comprised 40,000 foot and 7,000 horse. Caesar had fewer than half this number, 22,000 only, and of these a mere 1,000 were cavalry.

One flank rested on the River Enipeus, so this was secure against Pompey’s horse, but the other flank, Caesar’s right, was open. Here was the place of danger and decision.

Late Republican armies typically deployed in three lines, and so it was on this occasion. Pompey placed Afranius in command on the right, Scipio in command in the centre, and Pompey himself took station on the left, where, in addition to the legionaries forming the centre left, he deployed all his cavalry, archers, and slingers on the outer left.

These last were to be his masse de manoeuvre and principal strike-force. The cavalry, covered by showers of arrows and slingshot, were to sweep away Caesar’s thousand horsemen and then wheel into the right flank and rear of his foot, rolling up his army from right to left.

Caesar’s deployment

Caesar’s three lines were necessarily more extended than Pompey’s, for he had to match his enemy’s frontage with half the numbers. Lacking weight, he had to rely on the superior prowess of his Gallic War veterans to fix Pompey’s legions while the main action played out on the right.

Antony was given command on the left, by the river, Domitius in the centre, and Sulla on the right, where Caesar also took station, opposite Pompey, close to his crack troops, the Tenth Legion, and close to the battle’s intended schwerpunkt.

But there was something more: a supreme example of Caesar’s flexibility, imagination, and innovatory panache in tactical matters. He created a battle group of six cohorts, taken from the legions forming his third line, perhaps 3,000 men in all, and deployed them as a fourth line, but angled to face the right, as a flank defence.

This was his brilliantly simple solution to the problem posed by Pompey’s overwhelming superiority in cavalry. And this fourth line was not only a defensive device, it was tasked with mounting a fierce counter-attack to break the Pompeian left, chase it off the field, and then wheel in against the embattled centre.

The clash of legionaries

Pompey seems to have mishandled the clash of legionaries. He ordered his men to hold their ground and fight defensively. He seems to have done this for two reasons: to maintain the integrity of a shield-wall as a defence against the enemy’s shower of pila (javelins); and so that Caesar’s legionaries would have to cover twice the distance to reach them and would arrive winded and disordered.

Pompey was perhaps attempting to compensate for the comparative inexperience of his men. But the intended surprise was defeated by the exceptional discipline of Caesar’s veterans. Realising that Pompey’s line had remained stationary, the centurions halted the advance to redress the ranks and gather breath.

They then charged again, hurling pila to decimate the enemy line, then drawing gladii (short stabbing swords) for close-quarters action. Caesar was scathing about Pompey’s defensive stance:

It appears to us that he did this without sound reason, for there is a certain eagerness of spirit and an innate keenness in everyone which is inflamed by desire for battle. Generals ought to encourage this, not repress it. Nor was it for nothing that the practice began in antiquity of giving the signal on both sides and everyone’s raising a war-cry; this was believed both to frighten the enemy and to stimulate one’s own men.

Nonetheless, any Caesarian advantage was marginal. The Pompeian line held its ground, replied in kind to the enemy’s volleys, and then locked shields and drew swords for close-quarters confrontation.

The decision came not in the centre, but, as both commanders had anticipated, on the open flank.

Pompey’s cavalry attack

Pompey’s cavalry attack, backed by the missile-shooters, had precisely the effect everyone anticipated: the Caesarian cavalry was pushed back, the right flank of the Caesarian infantry was exposed, and the follow-up lines of Pompeian cavalry began to reform to assault it.

At this point, Caesar ordered his fourth line to counter-attack. The Pompeian cavalry was caught in disarray, as some units were pushing forwards against the enemy cavalry in front, while others were attempting to redeploy to attack the exposed flank of Caesar’s main line.

For infantry to charge cavalry was to break all the rules, but the disorder in the Pompeian ranks, the surprise achieved, the inherent inability of cavalry to fight defensively, and Caesar’s explicit instructions to use pila as handheld thrusting spears and to aim for the faces of the enemy horsemen were decisive. The Pompeian cavalry was broken by the sudden onslaught.

The fourth-line legionaries were transformed in an instant into Caesar’s masse de manoeuvre and key strike-force. They could not outpace the fleeing cavalry, but they were soon among the archers and slingers – men without armour, trained and equipped only to fight at a distance – and these were cut down in large numbers.

The fourth line then halted, reformed, and executed a devastating right hook, plunging into the exposed left flank and rear of Pompey’s main line.

The effect was doubled by Caesar’s order to his third line, waiting in reserve, to enter the fray, relieving the tired men of the first and second lines, throwing fresh troops suddenly into the frontal attack.

The effect was to shatter the whole of Pompey’s left and spread panic down the line. Caesar was clear about the sequence of events:

Caesar [he always wrote of himself in the third person] was not wrong in thinking that the victory would originate from those cohorts which had been stationed in a fourth line to counteract the cavalry, as he had declared in cheering on his men. For it was by these that the cavalry were repulsed, it was by these that the archers and slingers were massacred, and it was by these that the Pompeian left wing was surrounded and the rout started.

The finale and the accounting

Pompey, distraught at the rout, took horse and fled. Elements of his broken army rallied over the next day or two, but they surrendered when Caesar offered generous terms. The rest dispersed beyond recall. The Pompeian army was destroyed.

The Caesarians discovered that many among Pompey’s senatorial entourage had anticipated victory with great confidence, for the abandoned enemy camp was decked out for celebration. Caesar described the scene in withering tones:

In Pompey’s camp could be seen artificial arbours, a great weight of silver plate laid out, tents spread with fresh turf, those of Lucius Lentulus and several others covered with ivy, and many other indications of extravagant indulgence and confidence in victory. So it could easily be judged that they had had no fears for the outcome of the day, in that they were procuring unnecessary comforts for themselves.

The Caesarian army lost only 200 killed, though this included 30 centurions, whereas the Pompeians lost 15,000 killed and wounded, while more than 24,000 surrendered. The disproportion speaks volumes about the nature of ancient battle.

As long as lines held firm, close-quarters action was defensive and tentative, more a confrontation of shield-walls than the mêlée of duelling typically depicted in films, so that casualties were relatively light. Heavy losses occurred only when lines broke and men turned their backs, attempted to flee, and then found their egress blocked by the crush; at that point, thousands might be cut down in the panic-stricken stampede to escape.

Most of the East immediately declared for Caesar. Pompey sought refuge in Egypt, but he was murdered by associates eager to curry favour with the conqueror. Though Pompeian resistance continued – especially in Africa and Spain – and there was much hard campaigning to come before Caesar emerged as master of the Roman world in 45 BC, the decisive battle had been fought. Pharsalus – a tactical masterpiece by the man who was both Rome’s greatest general and also the leader of the Populares – sounded the death-knell of the Republic. •