Final War of the Roman Republic The final war of the Roman Republic , also known as Antony ' s civil war or the war between Antony and Octavian , was the last of the Roman civil wars of the republic , fought between Cleopatra ( assisted by Mark Antony ) and Octavian . After the Roman Senate declared war on the Egyptian queen Cleopatra , Antony , her lover and ally , betrayed the Roman government and joined the war on Cleopatra ’ s side . After the decisive victory for Octavian at the Battle of Actium , Cleopatra and Antony withdrew to Alexandria , where Octavian besieged the city until both Antony and Cleopatra committed suicide . Following the end of the war , Octavian brought peace to the Roman state that had been plagued by a century of civil wars . Octavian became the most powerful man in the Roman world and the Senate bestowed upon him the name of Augustus in 27 BC . Octavian , now Augustus , would be the first Roman Emperor and would transform the oligarchic / democratic Republic into the Roman Empire . The last Republican Civil War would mark the beginning of the Pax Romana , which remains the longest period of peace and stability that Europe has seen in recorded history . Political and military buildup . The Caesarians Octavian ( Caesar ' s principal , though not sole , heir ) , Mark Antony , and Marcus Lepidus under the Second Triumvirate had stepped in to fill the power vacuum caused by Julius Caesar ' s assassination . After the Triumvirate had defeated Marcus Junius Brutus and Gaius Cassius Longinus at the Battle of Philippi ( 42 BC ) and Lepidus was expelled from the Triumvirate ( 36 BC ) , Octavian and Antony were left as the two most powerful men in the Roman world . Octavian took control of the west , including Hispania , Gaul , Italia , and Africa . Antony received control of the east , including Graecia , Asia , Syria and Aegyptus . For a time , Rome saw peace . Octavian put down revolts in the west while Antony reorganized the east ; however , the peace was short lived . Antony had been having an affair with the queen of Egypt , Cleopatra . Rome , especially Octavian , took note of Antony ’ s actions . Since 40 BC , Antony had been married to Octavia Minor , the sister of Octavian . Octavian seized the opportunity and had his minister Gaius Maecenas produce a propaganda campaign against Antony . All of Rome felt astonished when they heard word of Antony ’ s " Donations of Alexandria . " In these donations , Antony ceded much of Rome ’ s territory in the east to Cleopatra . Cleopatra and Caesarion were crowned co - rulers of Egypt and Cyprus ; Alexander Helios was crowned ruler of Armenia , Media , and Parthia ; Cleopatra Selene II was crowned ruler of Cyrenaica and Libya ; and Ptolemy Philadelphus was crowned ruler of Phoenicia , Syria , and Cilicia . Cleopatra took the title of Queen of Kings and Caesarion took the title of King of Kings . In response , Octavian increased the personal attacks against Antony , but the Senate and people of Rome were not convinced . Octavian ’ s chance came when Antony married Cleopatra in 32 BC before he divorced Octavia . That action combined with information that Antony was planning to establish a second Senate in Alexandria created the perfect environment for Octavian to strip Antony of his power . Octavian summoned the Senate and accused Antony of anti - Roman sentiments . Octavian had illegally seized Antony ’ s will from the Temple of Vesta . In it , Antony recognized Caesarion as Caesar ' s legal heir , left his possessions to his children by Cleopatra , and finally indicated his desire to be buried with Cleopatra in Alexandria instead of in Rome . The Senators were not moved by Caesarion or Antony ’ s children but Antony ’ s desire to be buried outside of Rome invoked the Senate ’ s rage . Octavian , the natural politician he was , blamed Cleopatra and not Antony . The Senate declared war on Cleopatra , and Octavian knew that Antony would come to her aid . When Cleopatra received word that Rome had declared war , Antony threw his support to Egypt . Immediately , the Senate stripped Antony of all his official power and labeled him as an outlaw and a traitor . Octavian summoned all of his legions , numbered at almost 200 , 000 Roman legionaries . Cleopatra and Antony did the same , assembling roughly the same number in mixed heavy Roman and light Egyptian infantry . The War . Naval theater . By mid - summer of 31 BC , Antony maneuvered his army into Greece and Octavian soon followed . Octavian brought with him his chief military advisor and closest friend Marcus Vipsanius Agrippa to command his naval forces . Although the ground forces were comparable , Octavian ' s fleet was superior . Antony ' s fleet was made up of large vessels , but with inexperienced crews and commanders . Octavian ' s fleet of smaller , more maneuverable vessels was filled with experienced sailors . Octavian moved his soldiers across the Adriatic Sea to confront Antony near Actium . Meanwhile , Agrippa disrupted Antony ' s supply lines with the navy . Gaius Sosius commanded a squadron in Mark Anthony ' s fleet with which he managed to defeat the squadron of Lucius Arruntius and put it to flight , but when the latter was reinforced by Agrippa , Sosius ' s ally Tarcondimotus - the king of Cilicia - was killed and Sosius himself was forced to flee . Octavian decided not to attack and risk unnecessary losses . Instead , Octavian wanted to battle Antony by sea where his experienced sailors could dominate . In response , Antony and Octavian engaged in Fabian strategy until the time was right . As the summer ended and autumn began to set in , both Octavian and Antony settled for a battle of attrition . The strategy of delay paid dividends to Octavian , as morale sank and prominent Romans deserted Antony ' s cause . The first conflict of the war occurred when Octavian ' s general Agrippa captured the Greek city and naval port of Methone . The city had previously been loyal to Antony . Although Antony was an experienced soldier , he did not understand naval combat , which led to his downfall . Antony moved his fleet to Actium where Octavian ’ s navy and army had taken camp . In what would become known as the Battle of Actium , Antony , on September 2 , 31 BC , moved his large quinquereme s through the strait and into the open sea . There , Octavian ’ s light and maneuverable Liburnian ships drew in battle formation against Antony ’ s warships . Cleopatra stayed behind Antony ’ s line on her royal barge . A devastating blow to Antony ’ s forces came when one of Antony ’ s former generals delivered to Octavian Antony ’ s battle plan . Antony had hoped to use his biggest ships to drive back Agrippa ' s wing on the north end of his line , but Octavian ' s entire fleet stayed carefully out of range . Shortly after mid - day , Antony was forced to extend his line out from the protection of the shore , and then finally engage the enemy . Octavian ' s fleet , armed with better trained and fresher crews , made quick work of Antony ’ s larger and less experienced navy . Octavian ’ s soldiers had spent years fighting in Roman naval combat , where one objective was to ram the enemy ship and at the same time kill the above deck crew with a shower of arrows and catapult - launched stones large enough to decapitate a man . As the armies stood on either side of the naval battle , they watched as Antony was being outmatched by Agrippa . Seeing that the battle was going against Antony , Cleopatra ' s fleet retreated to open sea without firing a shot , leaving Antony to fight for himself . As a gap opened in Agrippa ' s blockade , she funneled through , and was soon closely followed by Antony ' s command ships . The commanders of Antony ' s land forces , which were supposed to follow him to Asia , promptly surrendered their legions without a fight . Antony retreated to a smaller vessel with his flag and managed to escape to Alexandria . By the end of the day , Antony ’ s entire fleet would lie at the bottom of the sea and the Roman world had witnessed the largest naval battle in almost 200 years . Land campaign . With Octavian now in control of nearly 72 legions ( approximately 450 , 000 men ) , he was left as the indisputable master of the Roman world . Although Octavian wanted to immediately pursue Antony and Cleopatra , many of his veterans wanted to retire and return to private life . Octavian allowed many of his longest serving veterans ( as many as 10 legions by some accounts ) to retire . Many of those legionaries could trace their service to Julius Caesar some 20 years earlier . After the winter ended , Octavian resumed the hunt . In the spring of 30 BC , Octavian rejected the idea of transporting his army across the sea and attacking Alexandria directly , and instead traveled by land through Asia . Antony had received much of his backing from Rome ’ s client kingdom s in the east . By marching his army by land , he ensured Antony could not regroup and cement his authority over the provinces . Meanwhile , Antony attempted to secure an army in Cyrenaica from Lucius Pinarius . Unfortunately for Antony , Pinarius had switched his loyalty to Octavian . When Octavian received word of this development , he ordered Pinarius to move his four legions east towards Alexandria while Octavian would move west . Trapped in Egypt with the remnant of his former army , Antony and Cleopatra bided their time awaiting Octavian ' s arrival . When Octavian and Pinarius arrived at Alexandria , they placed the entire city under siege . Before Octavian had arrived , Antony took the roughly 10 , 000 soldiers he had left and attacked Pinarius , unaware that he was outnumbered 2 to 1 . Pinarius destroyed what was left of Antony ’ s army with Antony escaping back to Alexandria before Octavian arrived . As Octavian approached with his legions , what remained of Antony ' s cavalry and fleet surrendered to Octavian . Most of Antony ’ s infantry surrendered without any engagement at this stage of the conflict , and Antony ' s cause was lost . Antony was forced to watch as his army and hopes of dominance in Rome were handed to Octavian . In honorable Roman tradition , Antony , on August 1 , 30 BC , fell on his sword . According to the ancients accounts however , he was not entirely successful and with an open wound in his belly , was taken to join Cleopatra , who had fled to her mausoleum . Here Antony succumbed to his wound and supposedly died in his lover ' s arms , leaving her alone to face Octavian . Cleopatra did not immediately follow Antony in suicide . Instead , in a last - ditch effort , Cleopatra opened negotiations with Octavian . Cleopatra begged Octavian to spare Caesarion ’ s life in exchange for willing imprisonment . Octavian refused . Within a week , Octavian informed Cleopatra that she was to play a role in Octavian ' s Triumph back in Rome . This role was " carefully explained to her " , while Caesarion was " butchered without compunction " . Octavian supposedly said " two Caesars are one too many " as he ordered Caesarion ' s death . According to Strabo who was alive at the time of the event , Cleopatra died from a self - induced bite from a venomous snake , or from applying a poisonous ointment to herself . With Cleopatra ' s death , the final war of the Republic was over . Aftermath . Within a month , Octavian was named Pharaoh , and Egypt became his personal possession . Octavian now controlled all of Rome ' s provinces and over 78 legions ( around 520 , 000 men in total ) . By executing Antony ' s supporters , Octavian finally brought a century of civil war to a close . Within a few years , Octavian was named Augustus by the Senate and given unprecedented powers . Octavian , now Augustus , merged the western and eastern halves of the Republic into the Roman Empire , with Augustus ruling it as the first Roman emperor . In the ensuing months and years , Augustus passed a series of laws that , while outwardly preserving the appearance of the Republic , made his position within it of paramount power and authority . He laid the foundations for what is now called the Roman Empire . From then on , the Roman state would be ruled by a Princeps ( first citizen ) ; in modern terms , Rome would from now on be ruled by Emperors . The Senate ostensibly still had power and authority over certain Senatorial provinces , but the critical border provinces , such as Syria , Egypt , and Gaul , requiring the greatest numbers of legions , would be directly ruled by Augustus and succeeding Emperors . With the end of the last Republican civil war , the Republic was replaced by the Empire . The reign of Augustus would usher in the golden era of Roman culture and produce a stability which Rome had not seen in over a century . With Rome in control of the entire Mediterranean world , a peace would reign in the Roman world for centuries after the death of Augustus : the so - called Pax Romana ( Roman Peace ) . The Empire that Augustus established would last in Western Europe until the fall of Rome in the 5th century AD . The Eastern part of the Roman Empire would also survive as the Byzantine Empire until the fall of Constantinople in AD 1453 .