Augustus

==== War with Sextus Pompeius ====
{{Further|Bellum Siculum}}
Sextus Pompeius threatened Octavian in Italy by denying shipments of grain through the Mediterranean Sea to the peninsula. Pompeius's own son was put in charge as naval commander in the effort to cause widespread famine in Italy.{{Sfn|Eder|2005|page=19}} Pompeius's control over the sea prompted him to take on the name ''Neptuni filius'', "son of [[Neptune (mythology)|Neptune]]".{{Sfn|Eck|Takács|2003|page=22}} A temporary peace agreement was reached in 39&nbsp;BC with the [[Pact of Misenum]]; the blockade on Italy was lifted once Octavian granted Pompeius Sardinia, [[Corsica]], Sicily, and the [[Peloponnese]], and ensured him a future position as consul for 35&nbsp;BC.{{Sfn|Eder|2005|page=19}}{{Sfn|Eck|Takács|2003|page=22}}

The territorial agreement between the triumvirate and Sextus Pompeius began to crumble once Octavian divorced Scribonia and married Livia on 17 January 38&nbsp;BC.{{Sfn|Eck|Takács|2003|page=23}} One of Pompeius's naval commanders betrayed him and handed over Corsica and Sardinia to Octavian. Octavian lacked the resources to confront Pompeius alone, so an agreement was reached with the Second Triumvirate's extension for another five-year period beginning in 37&nbsp;BC.{{Sfn|Scullard|1982|page=163}}{{Sfn|Eck|Takács|2003|page=24}}

[[File:Denarius Sextus Pompeius-Scilla.jpg|thumb|300px|A [[denarius]] of [[Sextus Pompeius]], minted for his victory over Octavian's fleet. Obverse: the place where he defeated Octavian, Pharus of [[Messina]] decorated with a statue of Neptune; before that galley adorned with aquila, sceptre & trident; MAG. PIVS IMP. ITER. Reverse, the monster [[Scylla]], her torso of dogs and fish tails, wielding a rudder as a club. Caption: PRAEF[ECTUS] CLAS[SIS] ET ORAE MARIT[IMAE] EX S. C.]]
In supporting Octavian, Antony expected to gain support for his own campaign against the [[Parthian Empire]], desiring to avenge Rome's [[Battle of Carrhae|defeat at Carrhae]] in 53&nbsp;BC.{{Sfn|Eck|Takács|2003|page=24}} In an agreement reached at [[Taranto|Tarentum]], Antony provided 120 ships for Octavian to use against Pompeius, while Octavian was to send 20,000 legionaries to Antony for use against Parthia. Octavian sent only a tenth of those promised, which Antony viewed as an intentional provocation.{{Sfn|Eck|Takács|2003|page=25}}

Octavian and Lepidus launched a joint operation against Sextus in Sicily in 36&nbsp;BC.{{Sfn|Eck|Takács|2003|pages=25–26}} Despite setbacks for Octavian, the naval fleet of Sextus Pompeius was almost entirely destroyed on 3 September by General Agrippa at the naval [[battle of Naulochus]]. Sextus fled to the east with his remaining forces, where he was captured and executed in [[Miletus]] by one of Antony's generals the following year. As Lepidus and Octavian accepted the surrender of Pompeius's troops, Lepidus attempted to claim Sicily for himself, ordering Octavian to leave. Lepidus's troops deserted him, however, and defected to Octavian since they were weary of fighting and were enticed by Octavian's promises of money.{{Sfn|Eck|Takács|2003|page=26}}

Lepidus surrendered to Octavian and was permitted to retain the office of ''[[pontifex maximus]]'' (head of the college of priests) but was ejected from the Triumvirate. His public career at an end, he effectively was exiled to a [[villa]] at [[Mount Circeo|Cape Circei]] in Italy.{{Sfn|Scullard|1982|page=164}}{{Sfn|Eck|Takács|2003|page=26}} The Roman dominions were divided between Octavian in the West and Antony in the East. Octavian ensured Rome's citizens of their rights to property in order to maintain peace and stability in his portion of the empire. This time, he settled his discharged soldiers outside of Italy, while also returning 30,000 slaves to their former Roman owners—slaves who had fled to join Pompeius's army and navy.{{Sfn|Eck|Takács|2003|pages=26–27}} Octavian had the Senate grant him, his wife, and his sister [[tribune of the plebs|tribunal]] [[Sovereign immunity|immunity]], or ''[[Sacrosanctity|sacrosanctitas]]'', in order to ensure his own safety and that of Livia and Octavia once he returned to Rome.{{Sfn|Eck|Takács|2003|pages=27–28}}