Militarily, Antony, who had served with Caesar during the Gallic Wars, was by far the ablest soldier of the Triumvirate and, we may assume, was in charge of planning the campaign. His first task was to prevent Brutus and Cassius from taking over Greece and bringing their fleet into the Adriatic before he had had a chance to transport his forces there and establish himself. So he sent across the Adriatic Sea an advance guard, which marched down the Via Egnatia past Philippi and through the Symbolon, until it reached two further passes that provided the only known routes to Asia. But this force was quickly outflanked and compelled to retire.
Brutus and Cassius moved on to Philippi and were delighted by what they found there. The two hills in front of the town on either side of the road, flanked by woods on their right and the marsh on their left, made a very strong defensive position. Here they would stand and wait for the triumvirs.
The two generals built a fortified camp on each hill, connected by a palisade. Their strategy was to deny Antony a set-piece battle. He would have to maintain long supply lines across Greece, and transport from Italy would be halted, or at least harried, by the republican navy, which would blockade the seaways. It would not be long before he and Octavian were short of food. Eventually they would simply have to retreat—but where to, if the escape route by sea to Italy was barred?
A happy portent conveyed a general sense of optimism. Two eagles flew down onto two silver eagles, pecked at them, and then perched on the standards. As they stayed there the decision was taken to feed them regularly. Fortune was smiling on the republican cause.
The triumvirs and their legions slipped through the republican blockade and disembarked at Dyrrachium, where Octavian fell sick and had to be left behind, his army staying with him. According to Agrippa and Maecenas, his boyhood friends, he was suffering from dropsy (a morbid accumulation of fluid in the body) on this occasion. What may be significant is that he tended to be indisposed at times of great personal crisis. An inexperienced military leader, Octavian was approaching a fearsome challenge and it is possible that his illness was psychosomatic in origin.
Antony rushed on toward Philippi and encamped on the plain a mile or so from Brutus and Cassius. Ditches, earthworks, and palisades were built, and wells sunk for drinking water. Antony was in a most unfavorable position, on low-lying land prone to flooding. He judged that by setting up residence contemptuously close to the freedom fighters, he would communicate a powerful impression of self-confidence that might dampen his opponents’ morale; but when an ambush he set for some enemy foragers failed, he and his men began to lose hope of victory.
Octavian’s health did not improve, but when he learned that things were not going well, he immediately set off for Philippi. He was as suspicious of his colleague as of the freedom fighters. As Dio commented:
[Octavian] heard of the situation and feared the outcome in either case—whether Antony, acting alone, should be defeated or should conquer; for in the first case, he felt that Brutus and Cassius would be in a stronger position to oppose him, or in the latter case, Antony certainly would be.
When Octavian arrived, he shared the same camp as Antony and his forces.
For a while, nothing much happened, except for a few sallies and skirmishes. On or about September 30, the two eagles on the freedom fighters’ standards unexpectedly flew off, a discouraging sign for them. On the following day, Antony decided that something had to be done to break the deadlock and force a battle. With typical Caesarian dash, he ordered a detachment of men to cut a way secretly through the marsh, building a causeway by means of which a substantial number of men could out-flank the left of Cassius’ position, cutting the freedom fighters’ supply line down the Via Egnatia to Neapolis. Tall reeds prevented the enemy from seeing what was going on over the ten days needed to complete the work. Then, one night Antony sent a force along the causeway to the dry land on the far side, where the party quickly established fortified outposts.
Cassius was astonished when he realized what had happened. Not to be outdone, he had a fortification wall built through the marsh, which bisected Antony’s causeway and cut off the legionaries in the outposts. Antony responded by leading his army to attack and demolish a palisade that ran between Cassius’ camp and the marsh, for which purpose they carried with them crowbars and ladders. Their mission then was to attack and destroy the camp.
Cassius’ men could hardly believe their eyes, for the maneuver seemed extraordinarily foolhardy. Brutus’ men were ready and armed; they were unable to resist turning to their left and charging Antony’s men as they marched past. Brutus’ army would have endangered itself if it had pressed this attack for too long, because it would have exposed its own side and rear to a possible counterattack by Octavian’s forces. Before this could happen, they changed course and attacked the camp of Antony and Octavian. Sweeping all before them, they captured it.
Antony at last had his battle. Although he understood the difficulties the triumvirs’ soldiers were facing in the plain, it was too risky to lead his troops back down the hill. So he pressed on. The best account of the engagement is written by Appian, but at this point his description goes out of focus. Antony easily and quickly broke through the palisade and stormed Cassius’ camp, which was lightly defended. He led the attack in person, but presumably did so with only a part of his army, the rest of which must have been fighting Cassius’ main force, drawn up (we may suppose) along the line of the palisade to the marsh. The republican legionaries were gradually pushed back, and then lost further heart when they saw their camp being taken and scattered in disorder. The cavalry galloped off in the direction of the sea.
It had been a bizarre day. Both sides had won—and both had lost. Brutus’ men were plundering Octavian’s camp, and Antony’s that of Cassius. As a further complicating factor, there had been little rain and tramping feet had raised great clouds of dust over the battlefield—the “fog of war” avant la lettre. The various victors and vanquished had no idea what had happened to their friends and colleagues. Having looted the camps, soldiers began to go back to find their units. In the gloom they did not know to which army other legionaries belonged. Appian writes that they “returned looking more like porters than soldiers, and even then they did not notice or see each other distinctly.”
This confusion had an unexpected and disastrous consequence. When Cassius had been driven back from his palisade, he retreated quickly with a few followers to the hill on which Philippi stood and from there looked down on the battle. Being nearsighted, he could hardly see the looting of his camp, while the dust prevented any of his entourage from determining how Brutus was doing at the far end of the battlefield.
A large body of cavalry was seen riding toward his position, and Cassius feared that it was the enemy. However, to make sure, he sent one of his staff, a certain Titinius, to reconnoitre. In fact, the horsemen had been sent by Brutus and when they recognized Titinius approaching, they shouted for joy. Some of them leaped off their horses, hugged Titinius, shook him by the hand, sang, and clashed their weapons as a sign of victory.
Cassius jumped to the wrong conclusion, thinking that Titinius had been taken prisoner and that Brutus had been defeated. He withdrew into an empty tent and made his armor-bearer, a freedman called Pindarus, accompany him. While Pindarus, guessing what would be asked of him, hesitated, a messenger ran up to say that Brutus was victorious and was sacking the enemy camp.
“Tell him I wish him total victory,” Cassius replied, according to Appian.
Then turning to Pindarus, he said: