These eastern campaigns proved M. Antony's undoing as they distracted him from Italy, weakened his forces, and made him ultimately appear a political and cultural turncoat. This was at the same time that Octavian was acting as the restorer of Rome, fighting Italian and southern Gaul brigands, engaging in urban renovation programs, etc. A major spoiler here was Cleopatra, the erstwhile lover of Caesar. After his death, she had returned to Egypt and assumed the crown. When M. Antony was in the East in 40, he had called on her to explain her actions; they had become lovers and she bore him two children. Shortly thereafter, the Parthians invaded Syria, advancing through Asia Minor as well as into Judaea. Parthinii invasions also began in Macedonia. These Antony drove back, and after Naulochus, he returned east, inviting Cleopatra to stay with him and repudiating Octavian's sister. He drove the Parthians out of the eastern territories, rearranged Asia Minor's provinces, and installed Herod as Judaea's king. In 36 he undertook an offensive against the Parthians. At Phraaspia he sustained initial victories, but his Armenian auxiliaries deserted, and the Parthians attacked his siege and baggage train, which Antony lost, along with 20,000 soldiers. A retreat was necessary. The defeat was a big blow. Antony was politically and financially weakened, with a depleted military. He also became more financially and emotionally dependent on Cleopatra, who had borne him a third son. In the donations of Alexandria, he named this son, Ptolemy Caesar, as the heir to Caesar's position. War between Octavian and M. Antony was now imminent.
In 33, the triumvirate came to a legal end. For the next year, Mark and Octavian engaged in mutual slander, with Mark seeming less roman all the time. The real break came in 32. By this time both contenders had blocs of supporters in the Senate. When Octavian came to address the Senate one day, 300 Antony supporters fled to the East, to join their leader. With these, Mark formed a government in exile in Asia Minor, and raised a thirty-legion army as well as a 500-ship fleet. In retaliation, Octavian released what he claimed was Mark's will. In it, Mark indicated that he intended to move the state's capital to Alexandria, and that he intended to be buried next to Cleopatra—the Queen of kings. This put him on treasonous ground, so Octavian could present himself as a savior of the Republic. Italian towns passed 'spontaneous' resolutions of support for Octavian, while the latter laid a 25% income tax to support his large forces. The final battle was in 31. Antony's forces were in Greece, and went south to the bay of Anbracia. While Octavian followed these units south, Mark's fleet went to Actium, where Agrippa blockaded Mark's forces. Then, all engagement stopped for two weeks. Mark finally decided on a naval battle. He divided his fleet into four squadrons, himself commanding the right flank. While he fought well, the other two dropped back, and the fourth, under Cleopatra's command, simply fled. Mark was defeated, with his ground forces surrendering two weeks later. Meanwhile, Mark and Cleopatra had fled for Egypt, and Octavian followed in 30. While the latter was in pursuit, Mark heard that Cleopatra had killed herself, so chose suicide, but ended up dying in Cleopatra's arms, as she had not tried to take her own life. When Octavian arrived in Egypt, he had Ptolemy Caesar killed, thereby extinguishing the Ptolemaic dynasty. Egypt was made Octavian's personal property and annexed to the Roman Empire. Arriving in Rome, Octavian was acclaimed with a triple triumph, after which he reduced the Roman army from sixty to twenty-eight legions. Veterans were accorded lands in over thirty colonies, the land for which was bought rather than expropriated. Antony's (living) supporters were given an amnesty.
Commentary
The first question that has to be asked is why did Caesar win the civil war with Pompei? Most basically, he was the better general of the two. His army was better and faster, allowing him always to be on the offensive, and allowing him in turn to always provide his (retiring) soldiers with the material bases for survival. In the post-Marius era, a general's ability to support his current and retired soldiers was paramount in determining his own survivability. As well, Caesar demonstrated repeatedly his ability to provide clemency to erstwhile opponents, and was thus able to a gather more supporters to his banners. Therefore, through growing army power, increasing finances, and patronage, Caesar ascended to the rank of the most powerful Roman warlord and obtained powerful supporters, made up of a coalition of some senators, growing numbers of mounted and wealthy equities from provincial Italian municipalities, as well as foot-soldiers and elites fro regions where his own reputation was based, such as Gaul. All the while, he could count on the support of centurions and veterans. While they made him great, he looked after them, and al these groups came together into the factio—Caesar's faction. Caesar was also unusual, in that he combined being a good general with great political and legislative skills, as well as excellent rhetorical capabilities.
Next, we must ask why he was killed. While the individual conspirators may have had individual, opportunist motives, in general terms, the assassins all felt they were acting to preserve the republic from growing tyranny and dictatorship of an individual who had made his writ stick by dint of armed force. Of course, Caesar's senatorial expansion had represented an attack on the exclusivity of the legislative body and its reduction to a rubber stamp. This greatly offended senatorial aristocracies going back hundreds of years. The irony here, though, is that from the days of Sulla, all had seen their own actions in the context of republic-restoration, not recognizing that a government suited to running the affairs of a large city-state was totally inadequate to the needs of a multi- continent empire with a changing socio-economic complexion.
In the same way, the second triumvirate could not last. After Caesar had put forward the model of one man ruling all, no one was likely to be interested in prolonged power sharing. More concretely at least between Octavian and Mark Antony, tension pervaded their relations. Mark Antony perceived himself as the true heir with the proper experience, and viewed Octavian as an inexperienced neophyte. Indeed, on the surface, the latter was hampered from the start. He was quite young, and had no military reputation or demonstrable martial skills. He also went on to only muddle through in these matters. Further, he was financially strapped from the very beginning of the contest, thanks to Mark Antony, and ran the risk of becoming the Senate aristocracy's creature in their ostensible quest to preserve the republic. Still, Octavian had the legitimacy of Caesar's will on his side, as well as a growing body of senators who saw Mark Antony as the preeminent threat to the republican order. These latter Octavian was well able to manipulate, just as he cultivate the masses and provincial equities in a way beyond Mark Antony's capacity.
Thus, trust was conspicuously absent from these two triumvir's relations. Preeminence was needed, and it was assumed to be obtainable through war. In this, Mark Antony had more lucrative enemies, but also faced more costly and more enervating campaigns. Conversely, Octavian perceived that it was now possible to obtain a good reputation without engaging in far-flung campaigns. People in Otaly and other parts of the Roman core were sick of war, and needed the reestablishment of law and order for human and material survival. Octavian held himself out as able to provide all this, as his settlement of ex-soldiers shows. Thus in addition to the conflict of two individuals, what emerged was the conflict of two political programs, Mark Antony's based on the old rules of power politics, and Octavian's resting on new concepts. With critical mass tending in Octavian's favor, it would have required superb generalship for Mark Antony to prevail, and he was caught short here, even though Octavian was not an exceptional commander and had to rely on allies such as Agrippa. It is important to remember, though, that while what was at stake was the recasting of Rome politically and somewhat sociologically, it is highly likely that none of the major protagonists had any idea that they were on the cusp of an historical hinge, and were all ostensibly fighting for the restoration of the republic as they conceived it. None of the leaders, by 30, were looking beyond the situation at hand.