The Battle of Forum Gallorum was fought on 14 April 43 BC between the forces of Mark Antony and legions loyal to the Roman Senate under the overall command of consul Gaius Pansa, aided by his fellow consul Aulus Hirtius. The untested Caesar Octavian (the future emperor Augustus) guarded the Senate's camp. The battle occurred on the Via Aemilia near a village in northern Italy, perhaps near modern-day Castelfranco Emilia.
Antony was attempting to capture the province of Cisalpine Gaul from its appointed governor, Decimus Brutus. Brutus was besieged by Antony in Mutina (modern Modena), just south of the Padus (Po) River on the Via Aemilia. The Roman Senate sent all its available forces to confront Antony and relieve Brutus. Hirtius and Octavian arrived near Mutina with five veteran legions, where they waited for Pansa, who was marching north from Rome with a further four legions of recruits. Antony had four veteran legions in addition to the troops that were besieging Mutina. Aware that he would soon be outnumbered, Antony sought to defeat his opponents in detail before they could link up. After failing to provoke a battle with Hirtius, Antony marched two of his legions between the two Senatorial armies and laid an ambush on Pansa's approaching recruits. Unknown to Antony, Pansa had already been joined by one of Hirtius' veteran legions and Octavian's praetorian cohorts.
Antony's forces caught Pansa's army by surprise on a narrow road surrounded by marshes. A bitter, bloody battle ensued, in which Antony's II and XXXV legions defeated Pansa's troops and forced them to retreat southwards. Pansa himself was severely wounded. Antony called off the pursuit of Pansa's broken army and began marching his jubilant troops back towards Mutina. Hirtius then arrived from the north with a single veteran legion, which crashed into Anthony's exhausted troops, taking two Roman eagles and 60 standards. Antony's victory was turned into a major defeat; he fell back with his cavalry to his camp outside Mutina.
After receiving a report of the battle, Marcus Tullius Cicero, a fierce adversary of the Antonian faction, pronounced in the Senate the Fourteenth Philippic, exalting the success and praising the two consuls and young Caesar Octavian. Nevertheless, the battle was not decisive and the campaign continued. The two armies fought again seven days later (21 April) at the Battle of Mutina, which forced Antony to abandon the siege of the city and retreat westward. Hirtius was killed in the fighting at Mutina; Pansa was still recovering from his wound at Forum Gallorum but died on 23 April in unexplained circumstances.
Background
After the assassination of Julius Caesar, Antony's relations with Caesar's adoptive heir Octavian and the rest of the Roman Senate broke down. At the start of the War of Mutina in late 44 BC, he moved to invest the homonymous city in an attempt to force Decimus Junius Brutus Albinus, the governor of Cisalpine Gaul, to give it up to him in accordance with an illegal law he had passed previously that year in June.
At the start of 43 BC, the moderate Caesarians Aulus Hirtius and Gaius Vibius Pansa became consuls. Through the early months of the year, Antony's relations with the Senate broke down. Supported by a heterogeneous coalition including Cicero, Octavian, and large potions of the Senate, the consuls were dispatched to relieve Decimus Brutus' forces at Mutina and go to war against Antony. The consuls marched north, joined by Octavian and his private army, which had been legitimised by a grant of imperium pro praetore.
Battle Mark Antony's plan of attack
In early March 43 BC, Hirtius and Caesar Octavian advanced along the Via Aemilia and reached Bononia; Mark Antony chose to fall back again. For the moment, he sought to strengthen the encircling front around Mutina to contain Decimus Brutus. In fact, neither Hirtius nor Octavian were seeking an immediate battle; they had two of Caesar's legions that had abandoned Antony and three legions of recalled veterans gathered by Octavian in Campania, but for the moment they were waiting for the other consul Vibius Pansa, who left Rome on 19 March, to return along the Via Cassia with four legions of recruits that had been quickly mobilized in January 43 BC.
When Mark Antony became aware of the approach and imminent concentration of his enemies, he set out to take the initiative and move on to the attack as soon as possible. At first, Antony tried to hasten the battle and gain a decisive victory against the forces of Hirtius and Octavian. After leaving a part of his troops behind to detain Decimus Brutus at Mutina, he brought up the bulk of his forces, consisting of four veteran legions and large contingents of cavalry, near his two opponents' camp, harassing them with continuous skirmishes. Hirtius and Octavian, however, did not leave their camp but continued to await Pansa's arrival.
Mark Antony then decided on a new plan: having learned of the arrival of scouts from Vibius Pansa's legions along the Via Aemilia from Bononia, Antony thought he could easily attack and destroy them with his veterans. He also counted on the arrival of three legions from the south, recruited by his capable lieutenant Publius Ventidius Bassus from among Caesar's veterans settled in Picenum. Antony decided to leave part of his forces under the command of his brother Lucius Antonius to hold Decimus Brutus in check, and engage Hirtius and Octavian with a feigned attack on their camp, while moving against Pansa's troops under cover of darkness with his best legions.
Because of the uneven and marshy terrain near Forum Gallorum through which the antagonists would have to pass, Mark Antony could not deploy his excellent cavalry forces, but decided to attack by sending Legiones II Gallica and XXXV into the marshes and deploying his praetorian cohorts and those of Marcus Junius Silanus along the main road (Via Aemilia) over the marshy ground. The legionaries were deployed in the shelter of the reeds of the marshes at the point where the main road was narrowest; cavalry units and light infantry moved forward along the Via Aemilia to harry Pansa's troops and draw them into the trap.
Caesar Octavian and Aulus Hirtius had expected the legions of Vibius Pansa to arrive before attacking the forces of Mark Antony. When they learned of the approach of the other consul's four legions, they attacked the legate Servius Sulpicius Galba, one of Caesar's killers, with the Caesarian veterans of the Legio Martia led by the energetic Decimus CarfulenusCarfulenus had served under Caesar in the Alexandrine War. He is cited as "a man of exceptional personality and field experience" . and the personal praetorian cohorts of Caesar Octavian and Aulus Hirtius. Carfulenus and Galba moved in the darkness eastwards along the Via Aemilia and passed through Forum Gallorum; Pansa and Carfulenus made a junction in the night of 14 April 43 BC and started marching at dawn along the road with the pugnacious Legio Martia, five cohorts of recruits, and the praetorian cohorts of Caesar Octavian and Hirtius. In the marshes on either side, the first signs of the enemy were spotted, and presently Antony's praetorian cohorts appeared to block the main road.
Battle in the marshes
The Legio Martia and Vibius Pansa's recruits suddenly stood threatened in front of and alongside Antony's legions. The experienced legionaries did not lose their cohesion, but accepted battle after sending back the cohorts of recruits that were deemed unsuitable for the fight by the Caesarian veterans of the Martia. While the praetorian cohorts of Antony and Caesar Octavian fought sharply along the main road, the Martia veterans split into two parts and, under the command of Pansa and Carfulenus, ran into the marshes to join the battle. Carfulenus led eight cohorts of the Legio Martia into the swampy soil to the right of Via Aemilia, while in the marshes on the left side of the road, the consul Pansa commanded the other two cohorts of the legion, reinforced by Aulus Hirtius' praetorian cohorts. Mark Antony's veterans of Legio XXXV attacked the eight cohorts of the Martia while the entire Legio II moved against the two cohorts under the command of Vibius Pansa to the left of Via Aemilia.
The fighting between the Caesarian veterans of both parties was dramatic and bloody; in his history, Appian describes the particular bitterness of the two parties to a fratricidal struggle. Mark Antony's Caesarians were angry at the defection of the legionaries of the Legio Martia, now allied with the Senate, while the latter legion wanted to take revenge for the decimations and other punishments inflicted on them at Brundisium. Both sides believed that they could obtain a decisive victory, as the veterans' military pride increased the fury of the fight.
The clash between the Caesarian veterans on the two sides took place in a dark silence: without battle-cries or exhortations, the legionaries fought hand-to-hand in a frontal collision between their massed ranks in the swamps and valleys. The legionaries' fratricidal carnage was interrupted only by short breaks used to tighten their formations. The veterans knew their job well; without the need for encouragement, they continued the struggle with tenacity and obstinacy. The mutual slaughter with drawn blades impressed Pansa's inexperienced recruits, who watched the deadly and silent action of the Caesarian legionaries on both sides.
This fierce battle between the veterans continued in the swamps, initially without decisive results. On the right wing, the eight cohorts of the Legio Martia under the command of Decimus Carfulenus managed slowly to gain ground, while Antony's Legio XXXV gradually retreated in good order. On the left wing, on the other hand, the other two cohorts of the Legio Martia and the praetorian cohorts of Hirtius, under Pansa's command, first offered a stiff resistance but then began gradually to fold before Antony's entire Legio II. The battle finally turned to the favour of Antony's forces: in the centre along the Via Aemilia, Antony and Silanus' praetorian cohorts prevailed in a brutal clash with Caesar Octavian's praetorian cohorts, which were completely destroyed.
In the marshes to the right of the highway, the legionaries of the Martia, who were isolated some 500 paces in advance, were threatened by Antony's Moorish cavalry; Decimus Carfulenus had fallen mortally wounded, and the veterans began to fall back while still repulsing the cavalry's assaults. Exhausted, the legionaries of Antony's Legio XXXV did not at first pursue the retreating enemy. In the marshes to the left of the Via Aemilia, the consul Vibius Pansa suffered a serious injury while fighting on the line; his wound from a javelin shook the two cohorts of the Legio Martia. While the injured consul was transferred to Bononia, the Antonian veterans of Legio II finally put the two cohorts to flight; they now began to fall back in disorder, sowing panic in the ranks of Pansa's raw recruits, whose two legions had been kept far back in reserve. At the sight of the apparent collapse of the veterans of the Legio Martia, the new recruits scattered, falling back to camp in disorder.