The Death of the Republic

The Spark of War: A Republic Divided

The Battle of Philippi was the bloody and inevitable consequence of the assassination of Julius Caesar on the Ides of March, 44 BC. That single, violent act split the Roman world into two irreconcilable factions. On one side were the Caesarians, determined to avenge their fallen leader. On the other were the self-styled Liberators, who claimed to have killed a tyrant to save the Republic. The stage was set for a final, decisive civil war.

The leaders of the conspiracy, Marcus Junius Brutus and Gaius Cassius Longinus, fled east to rally their forces. According to the historian Plutarch, Brutus wrote to Cassius to remember their real purpose: to restore freedom to their state. They moved quickly to consolidate their power across the eastern provinces. Cassius, a seasoned military commander, besieged and defeated Dolabella, the governor of Syria and, at the time, an ally of Mark Antony, in Laodicea. With Syria under his control, Cassius began to levy the vast resources of the region for the coming war, demanding a staggering 700-talent tribute from the Judeans. Meanwhile, back in Italy, Caesar’s loyalists were marshaling their strength. In 43 BC, Caesar’s adopted heir, Octavian, joined forces with Caesar’s most trusted second-in-command, Mark Antony, and another prominent general, Lepidus, to form the Second Triumvirate. Unlike the informal “First Triumvirate” of Caesar, Pompey, and Crassus, this was a legal, public entity formally titled triumviri reipublicae constituendae—”triumvirs for the restoration of the republic.” They were granted the power to make laws and appoint magistrates, and their primary, publicly stated goal was to pursue and destroy Caesar’s assassins. With their armies raised and their political authority secured, the Triumvirs turned their gaze east, setting their forces in motion towards the plains of Macedonia where the final confrontation would occur.

The primary land route connecting Asia to Europe was the Via Egnatia, a great Roman road that snaked through the rugged terrain of Macedonia and Thrace. Control of its mountain passes was the critical strategic objective for both armies; for the Liberators, it was their path of advance, and for the Caesarians, it was the key to blocking them.

Recognizing this, the Caesarians dispatched a vanguard force under generals Norbanus and Saxa. Their orders were simple: advance into Thrace and halt the Liberators’ westward progress. They first occupied the Corpili pass, but after being forced to retreat, they established a far more formidable defensive position at the Sapaei pass. This chokepoint, protected by mountains on one side and the sea on the other, was a natural fortress across the Via Egnatia, effectively sealing the only viable invasion route for a large army.

The Liberators, however, had fortune on their side. A local Thracian named Rhascuporis revealed a trackless path that led around the mountains, allowing Brutus and Cassius to bypass the fortified pass. It was a difficult, four-day march, but the flanking maneuver was not just clever, but essential for their survival. Upon learning that their position had been compromised and their line of retreat threatened, Norbanus and Saxa had no choice but to abandon their blockade and withdraw their forces to the city of Amphipolis. This retreat left the mountain passes open, allowing the Liberators to advance and seize a powerful defensive position of their own—the very ground on which the fate of the Republic would be decided.

While some ancient accounts, notably Appian’s, placed the battle to the west of the city of Philippi, a first-hand letter from Mark Antony to the Jewish high priest Hyrcanus provides a more strategically coherent picture. Antony’s description points to a location in the southeastern part of the plain, near Mount Symbolon, which commanded the approach from the east. This commanding position not only gated the Via Egnatia but also allowed them to threaten the flank and rear of any army that tried to bypass them using the alternate southern route around Mount Pangaion.

In his letter, Antony described the Liberators’ position as being on a site that was:

“…naturally favourable and walled in by mountains as far as the sea, so that the passage could be controlled through only one gate.”

Brutus established his camp on a northern hill, holding the right flank, while Cassius occupied a southern hill, commanding the left. The two camps were connected by a wall and a ditch, creating a fortified line that effectively gated the Via Egnatia. Their position was nearly impregnable, and their supply lines were secure, running a short distance to their port at Neapolis.

The Caesarian forces under Antony and Octavian, arriving later, were forced to take a far inferior position. They encamped on exposed low ground in the plain, with their own fortifications but without the benefit of natural terrain. Their logistical situation was also precarious; their supply base at Amphipolis was much farther away, and the Liberators’ fleet controlled the sea.

The relative strengths of the two armies were as follows:

• Caesarians (Antony & Octavian): 19 legions (approx. 110,000 legionaries) and 13,000 cavalry.
• Liberators (Brutus & Cassius): 17 legions (approx. 80,000 legionaries) and 20,000 cavalry.

Given their superior defensive position and secure logistics, Brutus and Cassius wisely preferred a war of attrition. The Caesarians, with their exposed position and strained supply lines, were compelled to force a decisive battle as soon as possible.

With the Liberators dug in, the tactical dilemma fell to Mark Antony. He had to break the stalemate and draw the enemy into a pitched battle they did not want. His solution was a risky maneuver to outflank Cassius and threaten his supply lines, forcing a confrontation. This decision triggered the First Battle of Philippi, which unfolded as two distinct but simultaneous engagements. The battle erupted on two fronts. On the southern flank, Antony launched a ferocious and successful assault on Cassius’s fortifications, storming the defenses, routing his troops, and capturing their camp. At the same time, Brutus’s soldiers to the north, seeing the action unfold and without waiting for formal orders, charged Octavian’s forces. They overwhelmed the Caesarian left flank and captured the Triumvirs’ camp. Octavian himself was not present, having been carried away from the camp earlier due to illness.

The battle was an operational stalemate, a victory for one wing of each army and a defeat for the other. But a fatal miscommunication, shrouded by the dust kicked up by nearly 200,000 men, sealed the fate of the Republican cause.

Cassius had retreated to higher ground after his line broke. Seeing his camp sacked and unable to see through the dust to Brutus’s side of the field, he dispatched a centurion to discover what had happened. When the centurion was slow to return, Cassius tragically misinterpreted the situation, believing Brutus had also been defeated and that all was lost. In despair, he took his own life.

His suicide deprived the Liberators of their most experienced and capable military commander. Despite the battle being a draw—with Caesarian losses estimated at 16,000 to the Liberators’ 8,000—the loss of Cassius was a blow from which they would never recover. With Brutus now in sole command, a tense interlude of three weeks settled over the battlefield before the final confrontation.

Following the first battle, the strategic situation remained unchanged. Brutus, aware of his logistical advantage, wished to continue the war of attrition, knowing that the Caesarian army was running low on supplies with winter approaching. Antony and Octavian, however, were desperate for a final, decisive battle. They employed a series of aggressive tactics to force Brutus’s hand.

Several factors ultimately compelled Brutus to abandon his strategy and offer battle. The Caesarians engaged in aggressive skirmishing and occupied a hill within missile range of his camp, creating constant pressure. Simultaneously, Brutus faced immense pressure from his own impatient officers and soldiers, who persuaded him to fight rather than wait. Compounding these issues was his fear that Antony would succeed in a new flanking maneuver that would completely sever his supply lines.

Relenting, Brutus marched his army onto the plain. To avoid being outflanked by the larger Caesarian force, he stretched his line thin. The second battle was a brutal, head-on clash. Antony’s forces relentlessly pushed forward, smashing the weakened enemy center. As Brutus’s line began to buckle, Antony’s troops exploited the breach, swinging around to attack the rear of the Republican formations. Assailed from the front and back, Brutus’s army broke and fled.

Brutus managed to retreat with his remaining forces to Philippi itself, where he was soon hemmed in by Antony’s men. With his army shattered and his cause lost, he saw no path forward. That night, on nearby high ground, he committed suicide. His death marked the definitive end of the conspiracy and the Republican cause. The battle’s aftermath was a slaughter of Rome’s elite, prompting the historian Velleius Paterculus to write:

“There was no other battle more blood-soaked in the slaughter of the most distinguished men.”

Among the fallen were the younger Hortensius, Cato the Younger’s son, Livius Drusus, Lucullus, and Sextus Quinctilius Varus. With the last of Caesar’s assassins defeated, Mark Antony was hailed by his victorious army as the “Hero of Philippi.” The Triumvirs’ victory annihilated the last vestiges of the old Republican elite and consolidated their absolute power, setting the stage for the final civil war between Antony and Octavian that would lead to the rise of the Principate. The battle was over, and with it, the Roman Republic had breathed its last.