The civil war between Antony and Octavian seemed assured of dwarfing even the massive conflict between Caesar and his Republican opponents. Both sides had massive armies at their disposal, and Antony added the support Rome's eastern client kings, including Cleopatra of Egypt. By mid-summer of 31 BC, Octavian's war against his rival, though popularly characterized as being against the Egyptian Queen, had worked itself into little more than a stalemate. Antony had marched his army into Greece where he planned to oppose Octavian's advance, and the two considerable forces began to take up position against one another.
While the armies were of relatively equal strength, Octavian's fleet was vastly superior. Antony's fleet was made up of large vessels, though with inexperienced crews and commanders. On the other hand, Octavian's fleet of smaller, more maneuverable vessels was under the command of Marcus Vipsanius Agrippa, the proven admiral who excelled in the war against Sextus Pompey. While Octavian crossed the Adriatic to confront Antony near Actium in Epirus, Agrippa menaced Antony's supply lines with the fleet. Octavian wisely refused to give battle with the army, and Antony did likewise at sea. As the summer waned, both armies seemed to settle in for a battle of attrition.
The stalemate was working decidedly in Octavian's favor. The presence of Cleopatra with the Roman army of Antony was making the loyalty of his men a considerable challenge. For Antony's men, facing the son of Caesar, a god, was bad enough, but facing a Roman army while under the influence of an Egyptian Queen seemed an impossible situation. Defections from all quarters of Antony's support, to Caesar's side, were occurring in massive numbers. Agrippa's blockade against Antony tightened, and disease swept through Antony's camp. Common legionaries, commanders and Senators switched sides as the inevitable victory for Octavian seemed only a matter of time. By the time the calendar approached September of 31 BC, only 3 Consular magistrates remained with Antony.
On September 2, 31 BC Antony desperately attempted a breakout with his fleet to escape the blockade and regroup in Egypt. With his large ships, he sailed out of the gulf of Actium and engaged Agrippa's prepared navy. Though Antony's under matched forces fought valiantly, they were simply unable to counter Agrippa's vast superiority. Under the watchful eye of both armies on land, and as the tide turned against Antony, Cleopatra seized an opportunity to flee the battle with her own ships that were held in reserve. 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 without a fight. Octavian stood as the master of the Roman world, east and west and to commemorate his victory, he founded the city of Nicopolis (City of Victory) on the site.
All was not over just yet, however. Trouble with Octavian's veterans forced him to abandon pursuit of his eastern rival, and final victory would be delayed for a year. Octavian also wisely decided to put an end to any chance for Antony to regain strength from eastern kings by marching through the eastern provinces rather than sail directly to Egypt. Meanwhile, Antony attempted to secure an army in Cyrene from L. Pinarius Scarpus, but Scarpus refused and offered loyalty to Octavian. Trapped in Egypt with what remained of his former army, Antony and Cleopatra bided their time awaiting Octavian's arrival. As Octavian marched through Asia, Syria and Judaea establishing his authority, Scarpus sailed to Cyrenaica and moved east towards Egypt to pinch Antony between a two-pronged front.