Caesar ' s Civil War The Great Roman Civil War ( 49 – 45 BC ) , also known as Caesar ' s Civil War , was one of the last politico - military conflicts in the Roman Republic before the establishment of the Roman Empire . It began as a series of political and military confrontations , between Julius Caesar ( 100 – 44 BC ) , his political supporters ( broadly known as Populares ) , and his legions , against the Optimates ( or Boni ) , the politically conservative and socially traditionalist faction of the Roman Senate , who were supported by Pompey ( 106 – 48 BC ) and his legions . After a four - year - long ( 49 – 45 BC ) politico - military struggle , fought in Italy , Albania , Greece , Egypt , Africa , and Hispania , Caesar defeated the last of the Optimates in the Battle of Munda and became " Dictator perpetuo " ( Perpetual Dictator ) of Rome . The changes to Roman government concomitant to the war mostly eliminated the political traditions of the Roman Republic ( 509 – 27 BC ) and led to the Roman Empire ( 27 BC – AD 476 ) . Pre - war politico – military situation . Caesar ' s Civil War resulted from the long political subversion of the Roman Government ' s institutions , begun with the career of Tiberius Gracchus , continuing with the Marian reforms of the legions , the bloody dictatorship of Lucius Cornelius Sulla , and completed by the First Triumvirate over Rome . The First Triumvirate ( so denominated by Cicero ) , comprising Julius Caesar , Crassus , and Pompey , ascended to power with Caesar ' s election as consul , in 59 BC . The First Triumvirate was unofficial , a political alliance the substance of which was Pompey ' s military might , Caesar ' s political influence , and Crassus ' money . The alliance was further consolidated by Pompey ' s marriage to Julia , daughter of Caesar , in 59 BC . At the conclusion of Caesar ' s first consulship , the Senate ( rather than granting him a provincial governorship ) tasked him with watching over the Roman forests . This job , specially - created by his Senate enemies , was meant to occupy him without giving him command of armies , or garnering him wealth and fame . Caesar , with the help of Pompey and Crassus , evaded the Senate ' s decrees by legislation passed through the popular assemblies . By these acts , Caesar was promoted to Roman Governor of Illyricum and Cisalpine Gaul . Transalpine Gaul ( southern France ) was added later . The various governorships gave Caesar command of an army of ( initially ) four legions . The term of his proconsulship , and thus his immunity from prosecution , was set at five years , rather than the customary one year . His term was later extended by another five years . During this ten - year period , Caesar used his military forces to conquer Gaul and invade Britain , without explicit authorisation by the Senate . In 52 BC , at the First Triumvirate ' s end , the Roman Senate supported Pompey as sole consul ; meanwhile , Caesar had become a military hero and champion of the people . Knowing he hoped to become consul when his governorship expired , the Senate , politically fearful of him , ordered he resign command of his army . In December of 50 BC , Caesar wrote to the Senate agreeing to resign his military command if Pompey followed suit . Offended , the Senate demanded he immediately disband his army , or be declared an enemy of the people : an illegal political bill , for he was entitled to keep his army until his term expired . A secondary reason for Caesar ' s immediate want for another consulship was delaying the inevitable senatorial prosecutions awaiting him upon retirement as governor of Illyricum and Gaul . These potential prosecutions were based upon alleged irregularities occurred in his consulship and war crimes committed in his Gallic campaigns . Moreover , Caesar loyalists , the tribunes Mark Antony and Quintus Cassius Longinus , vetoed the bill , and were quickly expelled from the Senate . They then joined Caesar , who had assembled his army , whom he asked for military support against the Senate ; agreeing , his army called for action . In 50 BC , at his Proconsular term ' s expiry , the Pompey - led Senate ordered Caesar ' s return to Rome and the disbanding of his army , and forbade his standing for election " in absentia " for a second consulship ; because of that , Caesar thought he would be prosecuted and rendered politically marginal if he entered Rome without consular immunity or his army ; to wit , Pompey accused him of insubordination and treason . Great Roman Civil War . Crossing the Rubicon . On 10 January 49 BC , leading one legion , the Legio XIII Gemina , General Julius Caesar crossed the Rubicon River , the boundary between the Cisalpine Gaul province , to the north , and Italy proper , to the south , a legally - proscribed action forbidden to any army - leading general . The proscription protected the Roman Republic from a " coup d ' état " ; thus , Caesar ' s military action began a civil war . This act of war on the Roman Republic by Caesar led to widespread approval amongst the Roman civilians , who believed him a hero . The historical records differ about which decisive comment Caesar made on crossing the Rubicon : one report is " Alea iacta est " ( usually translated as " The die is cast " ) . March on Rome and the early Hispanian campaign . Caesar ' s March on Rome was a triumphal progress ; yet , the Senate , ignorant of Caesar ' s being armed only with a single legion , feared the worst and supported Pompey , who , on grasping the Republic ' s endangerment , said : " Rome cannot be defended " , and escaped to Capua with his politicians , the aristocratic " Optimates " and the regnant consuls ; Cicero later characterised Pompey ' s " outward sign of weakness " as allowing Caesar ' s politico - military consolidation to achieve Roman dictatorship . Despite having retreated , in central - Italy , Pompey and the Senatorial forces disposed of at least two legions , some 11 , 500 soldiers ( he earlier had ordered Caesar return to Italy from Gaul ) , and some hastily - levied Italian troops commanded by Lucius Domitius Ahenobarbus ( Domitius ) . As Caesar progressed southwards , Pompey retreated towards Brundisium , initially ordering Domitius ( engaged in raising troops in Etruria ) to stop Caesar ' s movement on Rome from the direction of the Adriatic seaboard . Belatedly , Pompey ordered Domitius to retreat south also , and make junction with Pompey ' s forces . Domitius mostly ignored Pompey ' s orders , and , after being isolated and trapped near Corfinium was forced to surrender almost thirty cohorts of troops ( about three Legions ) , most of whom promptly joined Caesar ' s army . Pompey escaped to Brundisium , there awaiting sea transport for his legions , to Epirus , in the Republic ' s eastern Greek provinces , expecting his influence to yield money and armies for a maritime blockade of Italy proper . Meanwhile , the aristocrats ( the Optimates ) — including Metellus Scipio and Cato the Younger — joined Pompey there , whilst leaving a rear guard at Capua . Caesar pursued Pompey to Brundisium , expecting restoration of their alliance of ten years prior ; to wit , throughout the Great Roman Civil War ' s early stages , Caesar frequently proposed to Pompey that they , both generals , sheathe their swords . Pompey refused , legalistically arguing that Caesar was his subordinate and thus was obligated to cease campaigning and dismiss his armies before any negotiation . As the Senate ' s chosen commander , and with the backing of at least one of the current consuls , Pompey commanded legitimacy , whereas Caesar ' s military crossing of the Rubicon River frontier rendered him a " de jure " enemy of the Senate and People of Rome . Nevertheless , in March 49 BC , Pompey escaped Caesar at Brundisium , fleeing by sea to Epirus , in Roman Greece . Advantaging himself of Pompey ' s absence from the Italian mainland , Caesar effected an astonishingly fast 27 - day , north - bound forced march to destroy , in the Battle of Ilerda , Hispania ' s politically leader - less Pompeian army , commanded by the legates , Lucius Afranius ( Afranius ) and Marcus Petreius ( Petreius ) , afterwards pacifying Roman Hispania ; in campaign , the Caesarian forces — six legions , 3 , 000 cavalry ( Gallic campaign veterans ) , and Caesar ' s 900 - horse personal bodyguard — suffered 70 men killed in action , while the Pompeian forces lost 200 men killed and 600 wounded . Returned to Rome in December of 49 BC , Caesar was appointed dictator , with Mark Antony as his Master of the Horse . Caesar kept his dictatorship for eleven days , tenure sufficient to win him a second term as consul with Publius Servilius Vatia Isauricus as his colleague . Afterwards , Caesar renewed pursuit of Pompey , then in Roman Greece . Greek and African campaigns . At Brundisium , Caesar assembled an army of some 15 , 000 soldiers , and crossed the Strait of Otranto to Palaesta in Epirus ( modern Palase / Dhermi , Albania ) . In that time , Pompey considered three courses of action : ( i ) alliance with the King of Parthia , an erstwhile ally , far to the east ; ( ii ) invade Italy with his naval superiority ; and ( iii ) confronting Julius Caesar in decisive battle . A Parthian alliance was unfeasible , a Roman general fighting Roman legions with foreign troops was craven ; and the military risk of an Italian invasion was politically unsavoury , because , the Italians ( who thirty years earlier had rebelled against Rome ) might rise against him ; thus , on councilor ' s advice , Pompey decided to fight Julius Caesar in decisive battle . Moreover , Caesar ' s pursuing him to Illyrium , across the Adriatic Sea , decided the matter , and , on 10 July 48 BC , Pompey fought him in the Battle of Dyrrhachium , costing Caesar 1 , 000 veteran legionaries and a retreat . Disbelieving that his army had bested Caesar ' s legions , Pompey misinterpreted the retreat as a feint to a trap , and refused to give chase for the decisive , definitive " coup de grâce " , thus losing the initiative , and the chance to quickly conclude Caesar ' s Civil War ; meanwhile , Caesar retreated southwards . Near Pharsalus , Caesar pitched a strategic bivouac , and Pompey attacked , yet , despite his much larger army , was conclusively defeated by Caesar ' s troops . A major reason for Pompey ' s defeat was a miscommunication among front cavalry horsemen . Egyptian dynastic struggle . Pompey fled to Egypt , where he was murdered by an officer of King Ptolemy XIII . Caesar pursued the Pompeian army to Alexandria , where they camped and became involved with the Alexandrine civil war between Ptolemy and his sister , wife , and co - regnant queen , the Pharaoh Cleopatra VII . Perhaps as a result of Ptolemy ' s role in Pompey ' s murder , Caesar sided with Cleopatra ; he is reported to have wept at the sight of Pompey ' s head , which was offered to him by Ptolemy ' s chamberlain Pothinus as a gift . In any event , Caesar was besieged at Alexandria and after Mithridates relieved the city , Caesar defeated Ptolemy ' s army and installed Cleopatra as ruler , with whom he fathered his only known biological son , Ptolemy XV Caesar , better known as " Caesarion " . Caesar and Cleopatra never married , due to Roman law that prohibited a marriage with a non - Roman citizen . War against Pharnaces . After spending the first months of 47 BC in Egypt , he went to Syria , and then to Pontus to deal with Pharnaces II , a client king of Pompey ' s who had taken advantage of the Romans being distracted by their civil war to oppose the Roman - friendly Deiotarus and make himself the ruler of Colchis and lesser Armenia . At Nicopolis he had defeated what little Roman opposition Caesar ' s lieutenant , the governor of Asia Gnaeus Domitius Calvinus could muster . He had also taken the city of Amisus , which was a Roman ally , made all the boys eunuchs and sold the inhabitants to slave traders . After this show of strength against the Romans , Pharnaces drew back to suppress revolt in his new conquests . Nevertheless , the extremely rapid approach of Caesar in person forced Pharnaces to turn his attention back to the Romans . At first , recognizing the threat , he made offers of submission , with the sole object of gaining time until Caesar ' s attention fell elsewhere ; Caesar ' s speed brought war quickly and battle took place near Zela ( modern Zile in Turkey ) , where Pharnaces was routed with just a small detachment of cavalry . Caesar ' s victory was so swift and complete that , in a letter to a friend in Rome , he famously said of the short war , " Veni , vidi , vici " ( " I came , I saw , I conquered " ) : indeed , for his Pontic triumph , that may well have been the label displayed above the spoils . Pharnaces himself fled quickly back to the Bosporus , where he managed to assemble a small force of Scythia n and Sarmatian troops , with which he was able to gain control of a few cities ; however , a former governor of his , Asandar , attacked his forces and killed him . The historian Appian states that Pharnaces died in battle ; Dio Cassius says Pharnaces was captured and then killed . Later campaign in Africa and the war on Cato . Caesar returned to Rome to deal with several mutinous legions . While Caesar had been in Egypt installing Cleopatra as Queen , four of his veteran legions encamped outside of Rome under the command of Mark Antony . The legions were waiting for their discharges and the bonus pay Caesar had promised them before the battle of Pharsalus . As Caesar lingered in Egypt , the situation quickly deteriorated . Antony lost control of the troops and they 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 he needed these legions to deal with Pompey ' s supporters in north Africa , who had mustered 14 legions of their own . 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 reenlist 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 . Caesar 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 that they would all be discharged immediately . He said he would pay them the money he owed them after he won the north African campaign with other legions . The soldiers were shocked . 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 suffer to bring them along , a huge cheer arose from the assembled troops . Through this reverse psychology , Caesar reenlisted four enthusiastic veteran legions to invade north Africa without spending a single sesterce . Caesar quickly gained a significant victory at Thapsus in 46 BC over the forces of Metellus Scipio , Cato the Younger and Juba ( who all committed suicide ) . Second Hispanian campaign and the end of the 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 ) escaped to Hispania . Caesar gave chase and defeated the last remnants of opposition in the Munda in March 45 BC . During this time , Caesar was elected to his third and fourth terms as consul in 46 BC ( with Marcus Aemilius Lepidus ) and 45 BC ( without colleague ) . Aftermath . Caesar was later proclaimed dictator first for ten years and then in perpetuity . The latter arrangement in openly doing away with a term limit , triggered the conspiracy leading to his assassination on the Ides of March in 44 BC out of such fears . Following this , Antony and Caesar ' s adopted son Octavius ( later Caesar Augustus ) had to fight yet another civil war against remnants of the Optimates and Liberatores faction , but they were crushed by the skill of Marcus Antonius , who was able to defeat his two main opponents , and Octavius , despite having his camp overrun , evaded capture .