In early 41 BC, Octavian returned to Italy from Philippi and was hard at work attempting to settle 40,000 veterans. He had a major problem in this task: a promise made that the legionaries would receive rich and fertile land around 18 major cities in Italy. This was an issue because the current inhabitants would have to be displaced, certainly a cause for serious social disorder. Compounding the problem was dissatisfaction among the troops who always felt that they weren't receiving what was promised. Among those dispossessed of home and property were the poets Virgil and Horace, the latter of whom served Brutus as a Tribune in his army. Those who had land confiscated were not compensated in any way, and anger against Octavian was growing to a cascade.
Lucius Antonius, brother of Mark Antony, sought to take advantage of the situation for his own, and most likely his brother's advantage. Though Antony seemingly had no involvement, he certainly hoped to gain at Octavian's expense. At the height of resentment against Octavian, Lucius and Antony's wife Fulvia, began to champion the cause of those who had been effected by Octavian's plan. Adding to the fuel, they began to spread the idea that Antony's troops were being under compensated in the whole affair in comparison to Octavian's own men. Some of Antony's men arranged a meeting between Octavian and Lucius to settle the affair, but a fight broke out between troops from both sides who went to the site ahead of their leaders.
Lucius gathered the forces loyal to Antony and marched on Rome, and Octavian was forced to withdraw to Etruria where he could prepare his men. Lucius quickly realized that his position was untenable and decided to head north to Cisalpine Gaul, where he could join with and coordinate with his brother's generals there. Octavian, however, wouldn't allow this to happen. He was faced with a serious threat from Sextus Pompey in Sicily, Lucius Antonius right in Italy, Antony's men in Gaul, and perhaps Antony himself from the east. Octavian cut off Lucius' retreat and besieged him at Perusia, effectively eliminating the threat of coordination with Antony's men in Gaul. After a short siege, Lucius realized that help was not going to come, and rather than starve to death, was forced to surrender.
By February of 40 BC, the so-called Perusine War ended as Lucius gave up the town. Likely fearing reprisal from his fellow triumvirate, Octavian took no action against Lucius, or Antony's wife Fulvia, but exacted revenge on the town itself instead. While Lucius was pardoned, the town magistrates were put to the sword (save for one who had supported the condemnation of Caesar's assassins some years prior), and the town was opened up to his men. At first Antony seemed to have little reaction to these events that took nearly a year to materialize. In the interim, however, Antony's governor in Gaul had died, and Octavian moved in to establish his own control of the province. While Antony, for the most part, ignored the trouble stirred up between his brother and Octavian, he had to respond to the loss of a major territorial stronghold.
By spring of 40 BC, Antony sailed to Brundisium in Italy's heel, but was refused entry by Octavian's garrison commander. Rather than be turned away, Antony besieged the city, and Octavian was forced to move south to meet this new threat. In the meantime, Antony had reconciled with the remaining Republicans under Sextus Pompey, and now it seemed that war was inevitable with a clear advantage going to Antony. Things looked so bleak for Octavian that he divorced his wife Claudia (step-daughter of Antony) and married Pompey's sister-in-law, apparently in an attempt to keep Sextus out of any coming fight between the two triumvirs. At this point, however, as the two armies prepared to meet near Brundisium, Anotny found that his men didn't have the stomach to do battle with their comrades, and Caesar's heir. Forced into negotiation, Octavian's future was saved by Antony's own men, and war was diverted, at least temporarily.
As a result of a new agreement between them (the Pact of Brundisium), both men confirmed the situation as the status quo. Octavian was ceded Gaul and Antony was reaffirmed as supreme commander in the entire east. Lepidus, the third member of the so-called triumvirate still languished as a bit player in Africa, and clearly fell behind his rivals for the ultimate power in the Roman world. As luck would have it, Antony's wife Fulvia died shortly after her involvement in the Perusine War, and Antony was free to remarry. Cementing their alliance, Antony married Octavian's sister, Octavia, and the two returned to Rome together and amidst a great deal of relief by the masses. They began to make plans to procure their own global dominance; Antony certainly wanting to return east where he hoped for his own campaign against the Parthians, and Octavian wanted to deal with Sextus Pompey once and for all.