Caesar's Civil War (49–45 BC) was one of the last politico-military conflicts of the Roman Republic before its reorganization into the Roman Empire.
It began as a series of political and military confrontations between Gaius Julius Caesar and Gnaeus Pompeius Magnus.
Prior to the war, Caesar had led an invasion of Gaul for almost ten years.
A build-up of tensions starting in late 49 BC, with both Caesar and Pompey refusing to back down led, however, to the outbreak of civil war.
Eventually, Pompey and his allies induced the senate to demand Caesar give up his provinces and armies.
Caesar refused and instead marched on Rome.
The war was a four-year-long politico-military struggle, fought in Italy, Illyria, Greece, Egypt, Africa, and Hispania.
Pompey defeated Caesar in 48 BC at the Battle of Dyrrhachium, but was himself defeated decisively at the Battle of Pharsalus.
Many former Pompeians, including Marcus Junius Brutus and Cicero, surrendered after the battle, while others, eg Cato the Younger and Metellus Scipio fought on.
Pompey fled to Egypt and was killed upon arrival.
Scipio was defeated in 46 BC at the Battle of Thapsus in North Africa.
He and Cato committed suicide shortly after the battle.
The following year, Caesar defeated the last of the Pompeians under his former lieutenant Labienus in the Battle of Munda and became dictator perpetuo (Dictator in perpetuity or Dictator for life) of Rome.Hornblower, S., Spawforth, A. (eds.)
The Oxford Companion to Classical Civilization (1998) pp.
219–24 Background
The main issue at hand in the lead-up to the war was how Caesar, who had been in Gaul for almost ten years prior to 49 BC, was to be re-integrated into the political fabric of Rome after accumulating immense power and wealth in Gaul..
"After the year 52, politics was dominated by the question of when and under what circumstances Caesar should return from Gaul".
Starting from 58 BC, the year after his consulship in 59, Caesar had held the proconsulship of Cisalpine Gaul along with Illyricum under the terms of the lex Vatinia and Transalpine Gaul at the assignment of the senate.
Caesar had allied himself with Crassus and Pompey in the so-called First Triumvirate during his consulship..
"It should... be stressed that... the political coalition sometimes misleading labelled the First Triumvirate was being put together by Caesar after his election and very shortly before he entered office" (emphasis in original).
The alliance of three men "induced a sharp restructuring of alliances and alignments" with temporary benefit to them but harm in the long-run with aristocratic groups coalescing in opposition.
The short-term benefits to the three emerged from their own purposes: ratification of Pompey's eastern settlement, agrarian measures involving Pompey and Crassus.
The political alliance between the three began to fray in the mid 50s BC but was put on hold with a renegotiation and the joint consulship of Pompey and Crassus in 55 BC.
Their joint consulship assigned new provincial commands to the consuls, with Pompey receiving Spain while Crassus went to Syria to fight the Parthians; Caesar, for his part, had his proconsulship in Gaul renewed.
After Crassus' departure from Rome at the end of 55 BC and following his death in battle in 53 BC, the alliance started to fracture more cleanly.
With the death of Crassus, and that of Julia (Caesar's daughter and Pompey's wife) in 54 BC, the balance of power between Pompey and Caesar collapsed and "a faceoff between [the two] may, therefore, have seemed inevitable".
From 61 BC, the main political fault-line in Rome was counterbalancing against the influence of Pompey, leading to his seeking allies outside the core senatorial aristocracy, i.e. Crassus and Caesar; but the rise of anarchic political violence from 55-52 BC finally forced the senate to ally with Pompey to restore order.
The breakdown of order in 53 and 52 BC was extremely disturbing: men like Publius Clodius Pulcher and Titus Annius Milo were "essentially independent agents" leading large violent street gangs in a highly volatile political environment.
This led to Pompey's sole consulship in 52 BC in which he took sole control of the city without convening an electoral assembly.
Political agitation to strip Caesar of his command and his legions had already started in the spring of 51 BC: M Claudius Marcellus argued in that year that the capture of Alesia and victory over Vercingetorix meant that Caesar's provincia (ie task) in Gaul was completed and therefore his command had lapsed.
He also argued that Caesar's expected desire to stand for a second consulship in absentia was not longer justified after his victory.
Regardless, the senate rejected Marcellus' motion, as well as his later motion to declare Caesar's term in Gaul to end on 1 March 50 BC.
At this time, Pompey was also instrumental in rejecting the proposed motions.
But after summer of 50, "positions had been hardened and events progressed irreversibly toward cataclysm", with Pompey now rejecting any Caesar's standing for a second consulship until he gave up his army and provinces.
The senate as a whole was relatively pacific, strongly supporting a proposal by Caesar's ally C Scribonius Curio who was then tribune of the plebs that both Pompey and Caesar give up their armies and commands.
The proposal passed in the senate by 370 in favour to 22 against on 1 December 50 BC, it was rejected by Pompey and the consul.
The consul, C Claudius Marcellus then seized upon rumours that Caesar was preparing to invade Italy and charged Pompey with defending the city and the republic.
One of the reasons given as to why Caesar decided to go to war was that he would be prosecuted for legal irregularities during his consulship in 59 BC and violations of various laws passed by Pompey in the late 50s, the consequence of which would be ignominious exile.
However, the prosecution theory emerging from Suetonious and Pollio is in "highly dubious territory" and "dubious in the extreme".
There is no evidence from the period 50-49 BC that anyone was seriously planning on putting Caesar on trial.
Caesar's choice to fight the civil war was motivated mostly stumbling in efforts to attain a second consulship and triumph, in which failure to do so would have jeopardised his political future.
Moreover, war in 49 BC was advantageous for Caesar, who had continued military preparations while Pompey and the republicans had barely started preparing.
Even in ancient times, the causes of the war were puzzling and perplexing, with specific motives "nowhere to be found".
Various pretexts existed, such as Caesar's claim that he was defending the rights of tribunes after they fled the city, which was "too obvious a sham".
Caesar's own explanation was that he would protect his personal dignitas; both Caesar and Pompey were impelled by pride, with Caesar refusing to "yield submissively to the blusterings of the conservatives, much less to the bullying of Pompey" in Gruen's words, and Pompey similarly refusing to accept Caesar's proposals, delivered as if they were directives.
There was little conscious desire for war until the last weeks of 50 BC, but "the boni had entrapped themselves... in a political vise from which they could not emerge with dignity except by aggressive self-assertion" while Caesar could not "permit [his status and reputation] to collapse through submission".
Civil War
For the months leading up to January 49 BC, both Caesar and the anti-Caesarians composed of Pompey, Cato, and others seemed to believe that the other would back down or, failing that, offer acceptable terms.
Trust had eroded between the two over the last few years and repeated cycles of brinksmanship harmed chances for compromise.
On 1 January 49 BC, Caesar stated that he would be willing to resign if other commanders would also do so but, in Gruen's words, "would not endure any disparity in their [Caesar and Pompey's] forces", appearing to threaten war if his terms were not met.
Caesar's representatives in the city met with senatorial leaders with a more conciliatory message, with Caesar willing to give up Transalpine Gaul if he would be permitted to keep two legions and the right to stand for consul without giving up his imperium (and, thus, right to triumph), but these terms were rejected by Cato, who declared he would not agree to anything unless it was presented publicly before the senate.
The senate was persuaded on the eve of war (7 January 49 BC) – while Pompey and Caesar continued to muster troops – to demand Caesar give up his post or be judged an enemy of the state.
A few days later, the senate then also stripped Caesar of his permission to stand for election in absentia and appointed a successor to Caesar's proconsulship in Gaul; while pro-Caesarian tribunes vetoed these proposals, the senate ignored it and moved the senatus consultum ultimum, empowering the magistrates to take whatever actions were necessary to ensure the safety of the state.
In response, a number of those pro-Caesarian tribunes, dramatising their plight, fled the city for Caesar's camp.
Crossing the Rubicon
On the 10th or 11th of January, Caesar crossed the Rubicon, a small river marking the boundary between the province of Cisalpine Gaul to the north and Italy proper to the south.
Crossing the Rubicon, Suetonius claims Caesar exclaimed Alea iacta est ("the die is cast"), though Plutarch maintains Caesar spoke in Greek quoting the poet Meander with aneristho kubos ("let the die be thrown"); Caesar's own commentaries do not mention the Rubicon at all.
This marked a formal start to hostilities, with Caesar being "undoubtedly a rebel".
On both sides, the rank and file soldiers followed their leaders: "the Gallic legions obeyed their patron and benefactor [who] deserved well of the res publica... others followed Pompey and the consuls [who] represented the res publica".
Caesar made sure to address his men: according to his own account, he spoke of injustices done to him by his political enemies, how Pompey had betrayed him, and but focused mostly on how the rights of tribunes had been trampled by the senate's ignoring tribunician vetoes, parading the tribunes who had fled the city before the troops in their disguises.
On the senatus consultum ultimum, Caesar argued it was unnecessary and should be confined only to circumstances in which Rome was under direct threat.
For most Romans, the choice of what side to pick was difficult.
Only a small number of people were committed to one side or the other at the onset of hostilities.
For example, Gaius Claudius Marcellus, who as consul in 50 BC had charged Pompey with defending the city, chose neutrality.
The then-young Marcus Junius Brutus, whose father had been treacherously killed by Pompey during Brutus' childhood, whose mother was Caesar's lover, and who had been raised in Cato the Younger's house, chose to leave the city, setting off a post in Cilicia and thence to Pompey's camp.
Caesar's most trusted lieutenant in Gaul, Titus Labienus also defected from Caesar to Pompey, possibly due to Caesar's hoarding of military glories or an earlier loyalty to Pompey.
March on Rome
Caesar's timing was far-sighted: while Pompey's forces actually vastly outnumbered Caesar's single legion, composing at least 100 cohorts, or 10 legions,Commentarii de Bello Civili, Caesar https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Caesar/Civil_Wars/1A*.html "by no stretch of the imagination could Italy have been described as prepared to meet an invasion".
Caesar captured Ariminum (modern day Rimini) without resistance, his men having already infiltrated the city; he captured three more cities in quick succession.
News of Caesar's incursion into Italy reached Rome around 17 January.
In response Pompey "issued an edict in which he recognized a state of civil war, ordered all the senators to follow him, [and] declared that he would regard as a partisan of Caesar any one who remained behind".
This led his allies to leave the city along with many uncommitted senators, fearing bloody reprisals of the previous civil wars; other senators simply left Rome for their country villas, hoping to keep a low profile.
In late January, Caesar and Pompey were negotiating, with Caesar proposing that the two of them return to their provinces (which would have required Pompey to travel to Spain) and then disband their forces.
Pompey accepted those terms provided that they withdraw from Italy at once and submit to arbitration of the dispute by the senate, a counter-offer that Caesar rejected as doing so would have put him at the mercy of a hostile senate while giving up all the advantages of his surprise invasion.
Caesar continued to advance.
After encountering five cohorts under Quintus Minucius Thermus at Iguvium, Thermus' forces deserted.
Caesar quickly overran Picenum, the area from which Pompey's family originated.
While Caesar's troops skirmished once with local forces, fortunately for him, the population was not hostile: his troops were refraining from looting and his opponents had "little popular appeal".
In February 49 BC, Caesar received reinforcements and captured Asculum when the local garrison deserted.
Only when he reached Corfinium did he encounter serious opposition led by Lucius Domitius Ahenobarbus, recently appointed governor of Gaul by the senate.
Pompey had urged Ahenobarbus to retreat south and join Pompey, but Ahenobarbus had responded with requests for support; regardless, Caesar prepared for a siege.
After Ahenobarbus received a letter from Pompey denying support, he claimed help was on the way but was caught planning an personal escape; in response, his men arrested him and sent envoys to surrender to Caesar after a short week-long siege.
Among the surrendered were some fifty senators and equestrians, all of whom Caesar allowed to go free.
When Corfinium's local magistrates handed over some six million sestertii that Ahenobarbus had brought to pay his men, Caesar returned it to the men and asked them to take an oath of loyalty, which they did.
Caesar's advance down the Adriatic coast was surprisingly clement and disciplined: his soldiers did not plunder the countryside as soldiers had during the Social War a few decades earlier; Caesar did not avenge himself on his political enemies as Sulla and Marius had done.
The policy of clemency was also highly practical: Caesar's pacificity prevented the population of Italy from turning on him.
At the same time, Pompey planned to escape east to Greece where he could raise a massive army from the eastern provinces.
He therefore escaped to Brundisium (modern Brindisi), requisitioning merchant vessels to travel the Adriatic.
Caesar pursued Pompey to Brundisium, arriving on 9 March with six legions.
By then, most of Pompey's forces had departed, with a rearguard of two legions waiting for transport.
While Caesar tried to block the harbour with earthworks and reopen negotiations, the earthworks were unsuccessful and Pompey refused to negotiate, escaping east with almost all of his men and all the ships in the region.
Spain and Africa
Following this setback and taking advantage of Pompey's escape east, Caesar marched west to Hispania.
While in Italy, he assembled a meeting of the rump senate on 1 April; turnout was poor.
There, Caesar repeated his grievances and requested senatorial envoys be sent to negotiate with Pompey; though the motion was passed, nobody volunteered.
A meeting of the concilium plebis also was called; although Caesar promised every citizen a gift of 300 sestertii and a guarantee of the grain supply, the reception was muted.
When one of the tribunes, L Caecilius Metellus interposed his veto against Caesar's attempt to raid the state treasury for funds, his veto was either ignored or his life threatened until he backed down.
This also showed the sham nature of Caesar's supposed casus belli in protecting the rights of tribunes: "the man who had proclaimed that he was championing the rights of the tribunes in January was now as ready as his opponents... [to] threaten one of these magistrates".
Caesar's raid captured some 15 thousand gold bars, 30 thousand silver bars, and 30 million sestertii, even seizing a special fund kept over the centuries to defend against Gallic attack.
Leaving Mark Antony in charge of Italy, Caesar set out west for Spain.
En route, he started a siege of Massilia when the city barred him entry and came under the command of Domitius Ahenobarbus.
Leaving a besieging force, Caesar continued to Spain with a small bodyguard and 900 German auxiliary cavalry.
He arrived in June 49 and at Ilerda he defeated a Pompeian army under legates Lucius Afranius and Marcus Petreius.
Pompey's remaining legate in Spain, Marcus Terentius Varro surrendered shortly thereafter, putting all of Spain under Caesar's control.
Concurrent to Caesar's invasion of Spain, he sent his lieutenant Curio to invade Sicily and Africa assisted by Gaius Caninius Rebilus, where his forces were decisively defeated in the Battle of the Bagradas River in August 49 BC.
Curio was killed in battle.
Returning to Rome in December 49 BC, Caesar left Quintus Cassius Longinus in command of Spain and had praetor Marcus Aemilius Lepidus appoint him dictator.
As dictator, he conducted elections for the consulship of 48 BC before using the dictatorial powers to pass laws recalling from exile those condemned by Pompey's courts in 52 BC, excepting Titus Annius Milo, and restoring the political rights of the children of victims of the Sullan proscriptions.
Holding the dictatorship would have been the only way to avoid giving up his imperium, legions, provincia, and right to triumph while within the pomerium.
Standing in the same elections he conducted, he won a second term as consul with Publius Servilius Vatia Isauricus as his colleague.
He resigned the dictatorship after eleven days.
Caesar then renewed his pursuit of Pompey across the Adriatic.
Greek and Macedonian campaign
Arriving at Brundisium, Caesar did not have enough transports to sail his entire force, meaning that multiple voyages across the Adriatic would be needed; this was complicated by a Pompeian fleet stationed on the eastern side of the Adriatic under the command of Marcus Calpurnius Bibulus.
Sailing on 4 January 48 BC – in reality, due to drift from the Roman calendar, late autumn – Caesar took the Pompeians by surprise, with Pompey's troops dispersed to winter quarters and Bibulus' fleet not ready.
Bibulus' fleet, however, quickly sprung into action and captured some of Caesar's transports as they returned to Brundisium, leaving Caesar stranded with some seven legions and little food.
Caesar then pushed to Apollonia with little local resistance, allowing him to secure a base and some food stores; seeing that the main Pompeian supply base was at Dyrrachium, Caesar advanced on it but withdrew when Pompey arrived first with superior forces.
After receiving the remainder of his army from Italy under Mark Antony on 10 April, Caesar advanced against Dyrrachium again, leading to the Battle of Dyrrachium.
After attempting circumvallation of the Pompeian defenders, Caesar attempted to capture the vital Pompeian logistics hub of Dyrrachium but was unsuccessful after Pompey occupied it and the surrounding heights.
In response, Caesar besieged Pompey's camp and constructed a circumvallation thereof, until, after months of skirmishes, Pompey was able to break through Caesar's fortified lines and force Caesar into a strategic withdrawal for Thessaly.
After the victory, seeking to spare Italy from invasion, prevent Caesar from defeating Scipio Nasica's forces arriving from Syria, and under pressure from his overconfident allies who accused him of prolonging the war to extend his command, Pompey sought to engage Caesar in a decisive battle.
After meeting up with Scipio Nasica's Syrian reinforcements, Pompey led his forces after Caesar in early August, seeking favourable ground for a battle.
After several days of cavalry skirmishes, Caesar was able to lure Pompey off of a hill and force battle on the plain of Pharsalus.
During the battle, a flanking manoeuvre led by Labienus failed against a reserve line of Caesar's troops, leading to the collapse of the Pompeian infantry against Caesar's veterans.
Shortly after the battle and sometime in October, Caesar was named dictator for the second time, for an entire year.
Pompey, despairing of the defeat, fled with his advisors overseas to Mytilene and thence to Cilicia where he held a council of war; at the same time, Cato's supporters regrouped at Corcyra and went thence to Libya.
Others, including Marcus Junius Brutus sought Caesar's pardon, travelling over marshlands to Larissa where he was then welcomed graciously by Caesar in his camp.
Pompey's council of war decided to flee to Egypt, which had in the previous year supplied him with military aid.
Egyptian dynastic struggle
When Pompey arrived in Egypt, he was greeted by a welcoming delegation made up of several Egyptians and two Roman officers who had served with him years before.
Shortly after boarding their boat, he was murdered in sight of his wife and friends on the deck.
Caesar pursued vigorously as Pompey's skill and client networks made him the largest threat; travelling first to Asia and then to Cyprus and Egypt, he arrived three days after Pompey's murder.
There, he was presented with the head of Pompey, along with his signet ring; Caesar wept when he saw the ring and recoiled from the head: "his disgust and sorrow may well have been genuine, for from the beginning he had taken great pride in his clemency".
Egypt by this time had been embroiled in repeated civil wars, also frequently arbitrated by Rome – helped in part due to the massive bribes Egyptian monarchs gave to Roman leaders – which eroded the realm's independence.
While in Egypt, Caesar started to get involved a dynastic dispute between Ptolemy XIII and Cleopatra, who in the will (registered in Rome) of the last Egyptian king (Ptolemy XII Auletes) had been made co-rulers.
By 48 BC, relations between the two co-rulers had broken down, with the two shadowing each other with armies on opposite sides of the Nile.
Caesar demanded a ten million denarii payment of a large debt promised to him by the previous king; a demand almost certainly motivated by the "massive financial commitments" needed to pay his troops; he also declared that he would arbitrate the succession dispute between Ptolemy XIII and Cleopatra.
In response, Pothinus (Ptolemy XIII's eunuch regent), apparently summoned an army to the city and besieged Caesar's occupation of the royal quarter; Caesar summoned reinforcements from Roman Asia.
While under siege in Alexandria, Caesar met Cleopatra and became her lover when she secreted herself into the royal quarter.
Around this time, Caesar also produced his decision on the dynastic dispute: the will's terms were clear and both would have to be co-rulers.
Ptolemy XIII impressed, probably already aware of Caesar and Cleopatra's relationship.
After some months of siege, Caesar's forces were relieved by forces under Mithridates of Pergamum from Syria, bringing the Egyptians to battle with Caesar's forces where the Egyptians were utterly routed.
Ptolemy XIII fled but drowned when his boat capsized.
After the victory, Caesar gave the Roman province of Cyprus to Egypt, likely secured payment of his financial demand, and invested Cleopatra (along with a new co-ruler Ptolemy XIV Philopator, Cleopatra's younger brother) with rule of Egypt.
While Caesar's Alexandrian War implies he left Egypt forthwith, he actually stayed for some three months cruising with Cleopatra along the Nile, mostly to rest and perhaps also partly to make clear Rome's support for Cleopatra's new regime.
News of a crisis in Asia persuaded Caesar to leave Egypt in the middle of 47 BC, at which time sources suggest Cleopatra was already pregnant.
He left behind three legions under the command of a son of one of his freedmen to secure Cleopatra's rule.
War against Pharnaces
Aware of the civil war, Pharnaces II desired to reclaim his father's lands lost during the Third Mithridatic War and promptly invaded large parts of Cappadocia, Armenia, eastern Pontus, and Lesser Colchis.
Roman sources paint him cruelly, ordering the castration of any captured Romans; these attacks were uncontested after Pompey stripped the east for troops until Caesar's legate Gnaeus Domitius Calvinus fought him unsuccessfully near Nicopolis in December 48 BC with a inexperienced force.
Caesar moved from Egypt north along the eastern Mediterranean coast, moving directly for Pharnaces' invasion, seeking to protect his prestige, which would suffer substantially if a foreign invasion were to go unpunished.
Pharnaces attempted to treat with Caesar, who rejected all negotiations, reminding him of his treatment of Roman prisoners.
Caesar demanded him to withdraw immediately from all occupied territories, return their spoils, and release all prisoners.
When the Romans arrived near the hilltop town of Zela, Pharnaces launched an all-out attack as the Romans were entrenching.
The attack caused confusion among Caesar's forces but they quickly recovered and drove Pharnaces' forces down the hill.
After a breakthrough on the Caesarian right, Pharnaces' army routed.
He fled back to his kingdom but was promptly assassinated.
The whole campaign had taken just a few weeks.
Caesar's victory was so swift that in a letter to a friend in Rome, quipped "Veni, vidi, vici" ("I came, I saw, I conquered"), a tag repeated on placards carried in his Pontic triumph; he also mocked Pompey for making his name fighting such weak enemies.
Africa and the war on Cato
While Caesar had been in Egypt and installed Cleopatra as sole ruler, four of his veteran legions encamped, under the command of Mark Antony.
The legions were waiting for their discharges and the bonus pay that Caesar had promised them before the Battle of Pharsalus.
As Caesar lingered in Egypt, the situation quickly deteriorated.
Antony lost control of the troops, who began looting estates south of the capital.
Several delegations of diplomats were dispatched to try to quell the mutiny.
Nothing worked, and the mutineers continued to call for their discharges and back pay.
After several months, Caesar finally arrived to address the legions in person.
Caesar knew that he needed the legions to deal with Pompey's supporters in North Africa since the latter had mustered 14 legions.
Caesar also knew that he did not have the funds to give the soldiers their back pay, much less the money needed to induce them to re-enlist for the North African campaign.
When Caesar approached the speaker's dais, a hush fell over the mutinous soldiers.
Most were embarrassed by their role in the mutiny in Caesar's presence.
He asked the troops what they wanted with his cold voice.
Ashamed to demand money, the men began to call out for their discharge.
Caesar bluntly addressed them as "citizens", instead of "soldiers," a tacit indication that they had already discharged themselves by virtue of their disloyalty.
He went on to tell them that they would all be discharged immediately.
He said that he would pay them the money that he owed them after he won the North African campaign with other legions.
The soldiers were shocked since they had been through 15 years of war with Caesar and they had become fiercely loyal to him in the process.
It had never occurred to them that Caesar did not need them.
The soldiers' resistance collapsed.
They crowded the dais and begged to be taken to North Africa.
Caesar feigned indignation and then allowed himself to be won over.
When he announced that he would allow them to join the campaign, a huge cheer arose from the assembled troops.
Through that reverse psychology, Caesar re-enlisted four enthusiastic veteran legions to invade North Africa without spending a single sesterce.
Caeser ordered twelve legions to gather in Lilybaeum on Sicily around late December.
He placed a minor member of the Scipio family at the front of his army because of the myth that no Scipio could be defeated in Africa.
The four veteran legions which had been involved in the mutiny were still in Campagnia, but six were ready in Lilybaeum.
A storm had scattered his transports and as a result he arrived with just 3000 infantry and 150 cavalry.
He tried to take Hadrumetum, but was forced to retreat to Ruspina because a large force of Optimates' cavalry arrived.
Caesar took the harbour city of Leptis where he was joined by some of his scattered troops.
A few days later new reinforcements arrived and with these he went on to the offensive.
A few miles from Ruspina he fought the inconclusive Battle of Ruspina.
Caesar withdrew to Ruspina, improved its defences and waited for more of his troops to arrive.
Meanwhile, the Optimates were gathering their forces near Hadrumetum to the north of Ruspina.
Eventually, the XIII and XIV legions arrived.
With these reinforcements Caesar went on the offensive.
He defeated the Optimates' Gallic and Germanic auxiliary cavalry in a skirmish near Ruspina.
In response the Optimates called on king Juba I of Numidia to join them with his army.
Caesar kept the initiative by marching on Uzitta, a major water source for the Optimates, and tried to force his enemy to battle.
Two more veteran legions, the IX and X, arrived bolstering his numbers.
The Optimates refused to engage on Caesar's terms so he retreated back to Ruspina.
Two more legions, the VII and VIII, arrived bringing up his numbers to twelve legions.
Supply problems forced Caesar to march his entire army south-west to forage.
The Optimates shadowed him with their army using their superior cavalry numbers to harass Caesar while foraging.
Caesar marched to and started to be besiege Thapsus trying to lure the Optimates into fighting a pitched battle.
The plan worked and Caesar quickly gained a significant victory at the Battle of Thapsus in 46 BC over the forces of Metellus Scipio, Cato the Younger and Juba, who all committed suicide.
Second Hispanian campaign and end of war
Nevertheless, Pompey's sons; Gnaeus Pompeius and Sextus Pompeius, together with Titus Labienus, Caesar's former propraetorian legate (legatus propraetore and second in command in the Gallic War) and Attius Varus, escaped to Hispania.
In Baetica, where most people were still adherents of Pompey, they started building an army.
In a few months time they were able to raise an army of several thousands of light infantry and cavalry, and more importantly four Roman legions.
These two legions which had defected from the governor of Hispanica Ulterior, Gaius Trebonius, a legion formed from the survivors of Thapsus, and an additional legion recruited from Roman citizens and local inhabitants.
They took control of almost all Hispania Ulterior, including the important Roman colonies of Italica and Corduba (the capital of the province).
Caesar sent two generals Quintus Fabius Maximus and Quintus Pedius with four legions to take care of the Pompeians, but because of the size of their opponents army they did not risk a battle and remained encamped at Obulco (present-day Porcuna), about  east of Corduba, requesting help from Caesar.
thumb|350px|Caesar's campaign to Munda Thus, Caesar was forced to move from Rome to Hispania to deal with the Pompeius brothers.
He brought three trusted veteran legions (X Equestris, V Alaudae and VI Ferrata)and one of the newer legions III Gallica, but in the main he was forced to rely on the recruits already present in Hispania.
Caesar covered the  from Rome to Obulco in less than one month, arriving in early December (he immediately wrote a short poem, Iter, describing this journey).
Caesar had called for his great-nephew Octavian to join him, but due to his health Octavian was only able to reach him after the conclusion of the campaign.
Ulia
When Caesar arrived in Baetica the Pompeians were laying siege to Ulia (one of the few towns which had remained loyal to Caesar).
Lucius Vibius Paciaecus, one of his officers who was known to the Ulians and knew the area, was sent with six cohorts (2,000-3,000 legionaries) to reinforce the defenders.
Caesar himself marched his main army on Corduba hoping to draw the Pompeians from Ulia.
Paciaecus arrived near Ulia during the night just when a storm swept in.
Using the darkness and the rain Paciaecus marched his men through the Pompeian lines, the sentries, unable to recognize the legionary symbols, let them pass.
Paciaecus slipped his men into the city reinforcing the defenders.
Corduba
While Ulia was being reinforced Caesar marched on towards Corduba which was defended by Sextus Pompeius and a strong garrison.
Onroute Caesar's vanguard clashed with Sextus' cavalry alerting the Pompeians to his presence.
Sextus sent word to his brother that Caesar was near Corduba and requested reinforcements.
Gnaeus gave up the siege of Ulia and marched to his brother's aid with the entire Pompeian army.
Sextus had blocked or destroyed the bridge to Corduba across the Baetis.
Caesar constructing a makeshift bridge and marched his army across setting up camp near Corduba.
Soon Gnaeus and Labienus arrived with the Pompeian army.
Fierce skirmishes were fought on the bridge, both sides losing many men.
Caesar was looking for a decisive engagement and this was not going to be it.
So during one night Caesar's army lit a great number of campfires to create the impression they were still in camp, slipped out, and after a daring river crossing, marched on Ategua.
Ategua
After arriving at the fortified city of Ategua Caesar began besieging it, building several camps around it.
Gnaeus and Labienus marched their army around Caesar's positions hoping to surprise him coming in from an unexpected direction.
They approached under the cover of a thick fog surprising a number of Caesar's pickets.
When the fog lifted it became clear Caesar had taken all the highground around the city and was entrenched very well.
Building a camp to the west (between Caesar and Ucubi) they tried to come up with a plan to dislodge their opponent from his superior position.
They launched an attack on the camp of Postumius and the XXVIII, but were repulsed when Caesar sent the V, VI and X to aid their comrades.
The following day Caesar was reinforced by his allies, most notably king Bogud of West-Mauretania.
Under Labienus’ advice, Gnaeus Pompeius decided to avoid an open battle, and Caesar was forced to wage a winter campaign, while procuring food and shelter for his army.
In early 45 BC the pro-Caesarian faction in Ategua offered to surrender the city to Caesar, but when the Pompeian garrison found out they executed the pro-Caesarian leaders.
The garrison tried to fight their way through Caesar's lines some time after the incident, but were beaten back.
The city surrendered soon after; this was an important blow to the Pompeian confidence and morale, and some of the native allies started to desert to Caesar.
Salsum and Soricaria
After taking Ategua Caesar started building a camp near the Pompeian camp across the River Salsum.
Gnaeus attacked quickly catching Caesar off guard.
The heroic actions and sacrifice of two centurions of the V stabilized the line.
After this setback Caesar decided to retreat to Sorecaria cutting of one of the Pompeian supply lines.
Another skirmish near Soricaria on March 7 went in Caesar's favor; many Romans in the Pompeian camp began planning to defect and Gnaeus Pompeius was forced to abandon his delaying tactics and offer battle.
He broke camp and marched his army south towards the town of Munda.
Munda
Caesar gave chase and on the 17th of March 45 BC the two armies met on the plains of Munda.
The Pompeian army was situated on a gentle hill, less than one mile (1.6 km) from the walls of Munda, in a defensible position.
Caesar led a total of eight legions (Legio II, III, V, VI, X, XXI, XXVIII and XXX), with 8,000 horsemen and an unknown number of light infantry, while Gnaeus commanded thirteen legions, 6,000 light-infantrymen, and about 6,000 horsemen.
Many of the Republican soldiers had already surrendered to Caesar in previous campaigns and had then deserted his army to rejoin Pompeius: they would fight with desperation, fearing that they would not be pardoned a second time (indeed Caesar had executed prisoners at his last major victory, at Thapsus).
After an unsuccessful ploy designed to lure the Pompeians down the hill, Caesar ordered a frontal attack (with the watchword "Venus", the goddess reputed to be his ancestor).
The fighting lasted for 8 hours without a clear advantage for either side, causing the generals to leave their commanding positions and join the ranks.
As Caesar himself later said he had fought many times for victory, but at Munda he had to fight for his life.Appian, Civil Wars, 104 Caesar took command of his right wing, where his favorite Legio X Equestris was involved in heavy fighting.
With Caesar's inspiration the tenth legion began to push back Pompeius' forces.
Aware of the danger, Gnaeus removed a legion from his own right wing to reinforce the threatened left wing, which was a critical mistake.
As soon as the Pompeian right wing was thus weakened, Caesar's cavalry launched a decisive attack which turned the course of the battle.
King Bogud and his Mauretanian cavalry attacked the Pompeian right breaking through the flank and attacking the rear of the Pompeian army.
Titus Labienus, commander of the Pompeian cavalry, saw this manoeuvre and moved some troops to intercept them.
The Pompeian army misinterpreted the situation.
Already under heavy pressure on both the left (from Legio X) and right wings (the cavalry charge), they thought Labienus was retreating.Cassius Dio, Roman History .
43.38 "Labienus, observing this, left his station and proceeded against him.
Pompey's men, then, supposing him to be in flight, lost heart; and though later, of course, they learned the truth, they could no longer recover themselves."
The Pompeian legions broke their lines and fled in disorder.
Although some were able to find refuge within the walls of Munda, many more were killed in the rout.
At the end of the battle there were about 30,000 Pompeians dead on the field;"In quo proelio ceciderunt milia hominum circiter XXX", De Bello Hispaniensi, 31 :"About 30.000 men fell in the battle" losses on Caesar's side were much lighter, only about 1,000."
Nostri desiderati ad hominum mille partim peditum, partim equitum, saucii ad D", De Bello Hispaniensi, 31: "On our side we had about 1000 missing between infantry and cavalry, 500 wounded" All thirteen standards of the Pompeian legions were captured, a sign of complete disbandment.
Titus Labienus and Attius Varus died on the field and were granted a burial by Caesar, while Gnaeus Pompeius managed to escape from the battlefield.
Meanwhile, Caesar had been elected to his third and fourth terms as consul in 46 BC (with Marcus Aemilius Lepidus) and 45 BC (sine collega, without a colleague).
Chronology
49 BC
January 1: The Roman Senate receives a proposal from Julius Caesar that he and Pompey should lay down their commands simultaneously.
The Senate responds that Caesar must immediately surrender his command.
January 10: Julius Caesar leads his 13th Legion across the Rubicon, which separates his jurisdiction (Cisalpine Gaul) from that of the Senate (Italy), and thus initiates a civil war.
February 15: Caesar begins the Siege of Corfinium against Lucius Domitius Ahenobarbus who held the city against Pompey's orders.
February 21: Corfinium is surrendered to Caesar after a bloodless week in which Ahenobarbus is undermined by his officers.
February: Pompey's flight to Epirus (in Western Greece) with most of the Senate, despite Caesar's siege of Brundisium in March
March 9: Caesar's advance against Pompeian forces in Hispania
April 19: Caesar's siege of Massilia against the Pompeian Lucius Domitius Ahenobarbus, later the siege was conducted by Caesarian Gaius Trebonius
June: Caesar's arrival in Hispania, where he was able to seize the Pyrenees passes defended by the Pompeian Lucius Afranius and Marcus Petreius.
July 30: Caesar surrounded Afranius and Petreius's army in the Battle of Ilerda
August 2: Pompeians in Ilerda surrendered to Caesar
August 24: Caesar's general Gaius Scribonius Curio, is defeated in North Africa by the Pompeians under Attius Varus and King Juba I of Numidia in the Battle of the Bagradas River, and commits suicide.
September: Decimus Junius Brutus Albinus, a Caesarian, defeated the combined Pompeian-Massilian naval forces in the naval Battle of Massilia, while the Caesarian fleet in the Adriatic was defeated near Curicta (Krk)
September 6: Massilia surrendered to Caesar, coming back from Hispania
October: Caesar appointed Dictator in Rome; presides over his own election as consul and resigns after eleven days
48 BC:
January 4: Caesar landed at Caesar's Beach in Palasë (Palaeste)
March: Marcus Antonius joined Caesar
July 10: Battle of Dyrrhachium, Julius Caesar barely avoids a catastrophic defeat by Pompey in Macedonia, he retreats to Thessaly.
August 9: Battle of Pharsalus: Julius Caesar decisively defeats Pompey at Pharsalus and Pompey flees to Egypt.
September 28: Caesar learned that Pompey was assassinated.
Siege of Alexandria
December: Pharnaces II, King of Bosporus, defeated the Caesarian Gnaeus Domitius Calvinus in the Battle of Nicopolis (or Nikopol)
December: Battle in Alexandria, Egypt between the forces of Caesar supported by his ally Cleopatra VII of Egypt and those of rival King Ptolemy XIII of Egypt and Queen Arsinoe IV.
During the battle part of the Library of Alexandria catches fire and is partially burned down.
Caesar is named Dictator for one year.
47 BC
February: Caesar and his ally Cleopatra defeat the forces of her rivals Egyptian King Ptolemy XIII and Queen Arsinoe IV in the Battle of the Nile, Ptolemy was killed, Caesar then relieved his besieged forces in Alexandria.
Caesar makes Cleopatra joint-ruler of Egypt with her younger brother Ptolemy XIV.
May: Caesar defeated Pharnaces II in the Battle of Zela.
(which Caesar tersely described as veni, vidi, vici.)
Pharaoh Cleopatra VII of Egypt promotes her younger brother Ptolemy XIV of Egypt to co-ruler.
August, Caesar quelled a mutiny of his veterans in Rome.
October, Caesar's invasion of Africa, against Metellus Scipio and Labienus, Caesar's former lieutenant in Gaul
46 BC
January 4: Caesar narrowly escapes defeat by his former second in command Titus Labienus in the Battle of Ruspina; nearly 1/3 of Caesar's army is killed.
February 6: Caesar defeats the combined army of Pompeian followers and Numidians under Metellus Scipio and Juba in the Battle of Thapsus.
Cato commits suicide.
Afterwards, he is accorded the office of Dictator for the next ten years.
November: Caesar leaves for Farther Hispania to deal with a fresh outbreak of resistance.
Caesar, in his role as Pontifex Maximus, reforms the Roman calendar to create the Julian calendar.
The transitional year is extended to 445 days to synchronize the new calendar and the seasonal cycle.
The Julian Calendar would remain the standard in the western world for over 1600 years, until superseded by the Gregorian Calendar in 1582.
Caesar appoints his grandnephew Gaius Octavius his heir.
45 BC
January 1: Julian calendar goes into effect
March 17: In his last victory, Caesar defeats the Pompeian forces of Titus Labienus and Pompey the younger in the Battle of Munda.
Pompey the younger was executed, and Labienus died in battle, but Sextus Pompey escaped to take command of the remnants of the Pompeian fleet.
The veterans of Caesar's Legions Legio XIII Gemina and Legio X Equestris demobilized.
The veterans of the 10th legion would be settled in Narbo, while those of the 13th would be given somewhat better lands in Italia itself.
Caesar probably writes the Commentaries in this year
44 BC
Julius Caesar is named Dictator perpetuo ("dictator in perpetuity")
Julius Caesar plans an invasion of the Parthian Empire
Julius Caesar is assassinated on March 15, the Ides of March.
Aftermath
Caesar was later proclaimed dictator first for ten years and then in perpetuity.
The latter arrangement triggered the conspiracy leading to his assassination on the Ides of March in 44 BC.
Following this, Antony and Caesar's adopted son Octavian would fight yet another civil war against remnants of the Optimates and Liberatores faction before another civil war in which the Caesarian victors turned on each other, resulting in Octavian's victory the establishment of the Roman Empire.
References
Bibliography
Modern sources
Books
Articles
Primary sources
The Commentarii de Bello Civili (Commentaries on the Civil War), events of the Civil War until immediately after Pompey's death in Egypt.
De Bello Hispaniensi (On the Hispanic War) campaigns in Hispania
De Bello Africo (On the African War), campaigns in North Africa
De Bello Alexandrino (On the Alexandrine War), campaign in Alexandria.
External links
Lewis E 83 Historia belli civilis inter Caesarem et Pompeium at OPenn
