Caesar's invasion of Macedonia
The main contemporary source for the theatre of the conflict is Caesar's Commentarii de Bello Civili, which documents events from the start of the civil war in 49 BC to Pharsalus.
The account is, as expected from its authorship, partial to Caesar; further sources are Cicero's contemporary letters, and the later histories of Appian, Plutarch, and other imperial historians.
[1] The main reasons for his flight were the relative unpreparedness of his forces arrayed in Italy at the start of the civil war and the advantages moving to Macedonia would give him: "ready access to the massive resources of [the] eastern provinces... [in] an area where virtually every community and ruler was personally bound to him".
[1] This massive availability of resources meant that Pompey was able to quickly assemble large amounts of troops, money, ships, and supplies for his campaign.
He spent most of the year building and training his army opposite the Adriatic from Italy with the long-term goal of repeating Sulla's strategy of using the eastern provinces as a base from which to launch a counter-invasion.
[1] Caesar did not immediately follow on: the bulk of his forces in March 49 BC had not yet reached southern Italy and he, regardless, lacked a fleet with which to cross the Adriatic.
He chose instead to invade Pompey's Spanish provinces; he was successful and forced their surrender after the Battle of Ilerda in a summer campaign.
[2] Caesar's position in Italy was troubled by troop mutinies, "partly the product of a period of idleness", and he moved swiftly to take the initiative against Pompey.
[5][6] However, the news of the landing spread and Bibulus' fleet quickly mobilised to prevent any further ships from crossing, placing Caesar at a significant numerical disadvantage.
[12][non-primary source needed] With a large army and a little-improved food situation, Caesar calculated that staying on the defensive was impossible and moved to besiege Dyrrhachium.
Pompey's army responded by occupying and fortifying a hill outside the city called Petra, which also overlooked a natural harbour, allowing him to receive food for his men.
[10] After Caesar's departure from the Epirot coast and stripping of most of his coastal garrisons, Gnaeus Pompeius (homonymous son of Pompey) moved to retake the port of Oricum at the head of an allied fleet.
[15] Caesar's food situation, however, had not improved; it had deteriorated to the point where his men were subsisting on a carnivorous diet with the addition of some roots.
[17] While some of Caesar's officers "are supposed to have believed" that a counterattack would have driven the Pompeian forces to flight, the legate on the spot – Publius Cornelius Sulla[18] – demurred.
[20] The Caesarian prisoners were killed, apparently at the order of Titus Labienus, who had served as one of Caesar's legates in Gaul before defecting to Pompey at the start of the war.
Amid squabbling between the Pompeian coalition over consulships, accusations against Afranius of betrayal at Ilerda, and demands by Ahenobarbus to punish Caesarians and self-proclaimed neutrals in Italy, Pompey's command was fractured and increasingly pushed by political rather than military rationales.
Possibly to keep Cato away from influencing the settlement after a decisive engagement, he was sent to garrison Dyrrhachium as Pompey's army moved into southern Macedonia; there, Cicero joined him.
When Caesar ordered that the army pack up and leave, the Pompeian forces marched down the slope and onto a plain, offering battle.
[29] Pompey's forces were deployed relatively deep, which would have strengthened his men's cohesion at the cost of reducing the number of effectives on the front line.
[30] The plan was "simple... but reasonable enough, exploiting [Pompey's] advantage in numbers and especially the great superiority in cavalry that would have room to manoeuvre on the open plain.
As Labienus' attack proceeded, however, his cavalry lost order before being set upon by Caesar's reserve line, wielding their pila as spears.
[22] There, he was met with two Roman officers who had served with him in the east and were subsequently part of Aulus Gabinius' army which had intervened and then been stationed in Egypt from 55 BC.
Cicero declined the offer, refusing to fight in a war he had tried his utmost to prevent, and set sail for Italy with others who were willing to ask for and accept Caesar's pardon.
Commentators dispute whether his reaction was genuine: "a cynical observer might say that it was very convenient for Caesar to be able to transfer to foreign assassins the guilt of killing one of the greatest heroes in the history of the republic [Pompey]".
