Battle of Pharsalus - Prelude

Prelude

A dispute between Caesar and the Senate of Rome culminated in Caesar marching his army on Rome and forcing Pompey, accompanied by much of the Roman Senate, to flee from Italy to Greece in 49 BC where he could better conscript an army to face his former ally. Caesar, lacking a fleet to immediately give chase, solidified his control over the western Mediterranean – Spain specifically – before assembling ships to follow Pompey. Bibulus, whom Pompey had appointed to command his 600-ship fleet, set up a massive blockade to prevent Caesar from crossing to Greece and to prevent any aid to Italy. Caesar, defying convention, chose to cross the Adriatic during the winter, with only half his fleet at a time. This move surprised Bibulus and the first wave of ships managed to run the blockade easily. Now prepared, Bibulus managed to prevent any further ships from crossing, but died soon afterwards.

Caesar was now in a dire position, holding a beachhead at Epirus with only half his army, no ability to supply his troops by sea, and limited local support, as the Greek cities were mostly loyal to Pompey. Caesar's only choice was to fortify his position, forage what supplies he could, and wait on his remaining army to attempt another crossing. Pompey by now had a massive international army; however, his troops were mostly untested raw recruits, while Caesar's troops were hardened veterans. Realizing Caesar's difficulty in keeping his troops supplied, Pompey decided to simply mirror Caesar's forces and let hunger do the fighting for him. Caesar began to despair and used every channel he could think of to pursue peace with Pompey. When this was rebuffed he made an attempt to cross back to Italy to collect his missing troops but was turned back by a storm. Finally, Marc Antony rallied the remaining forces in Italy, fought through the blockade and made the crossing, reinforcing Caesar's forces in both men and spirit. Now at full strength Caesar felt confident to take the fight to Pompey.

Pompey was camped in a strong position just south of Dyrrhachium with the sea to his back and surrounded by hills, making a direct assault impossible. Caesar ordered a wall to be built around Pompey's position in order to cut off water and pasture land for his horses. Pompey built a parallel wall and in between a kind of no man's land was created, with fighting comparable to the trench warfare of World War I. Finally the standoff was broken by a traitor in Caesar's army, who informed Pompey of a weakness in Caesar's wall. Pompey immediately exploited this information and forced Caesar's army into a full rout, but ordered his army not to pursue, fearing Caesar's reputation for setting elaborate traps. This caused Caesar to remark, "The day was theirs had there been anyone among them to take it." Pompey continued his strategy of mirroring Caesar's forces and avoiding any direct engagements. After trapping Caesar in Thessaly, the prominent Senators in Pompey's camp began to argue loudly for a more decisive victory. Although Pompey was strongly against it - he wanted to surround and starve Caesar's army instead - he eventually gave in and accepted battle from Caesar on a field near Pharsalus.

Caesar had the following legions with him:

• Legions of veterans from the Gallic Wars – Caesar's favourite legion, X Equestris, and those later known with the names of VIII Augusta, IX Hispana, and XII Fulminata
• Legions levied for the civil war – legions later known as I Germanica, III Gallica, and IV Macedonica

However, all of these legions were 'short', and did not have the requisite numbers of troops. Some only had about a thousand men at the time of Pharsalus, due partly to losses at Dyrrhachium and partly to Caesar's wish to rapidly advance with a picked body as opposed to a ponderous movement with a large army.