Augustus defeated Sextus Pompeius

Sextus Pompeius, the son of Pompey the Great, was yet another significant thorn in the side of Augustus during his reign. Pompeius received Sicily and Sardinia after the Second Triumvirate in an effort to appease him and avoid any conflicts with the triumvirs. The marriage of Augustus to Scribonia, the sister or daughter of Pompeius' father-in-law Lucius Scribonius Libo, cemented the connection with Augustus.

By forbidding grain supplies from the continent over the Mediterranean Sea to Italy, Sextus Pompeius endangered Augustus. To spread starvation throughout Italy, Pompeius' own son was assigned the position of a naval commander. As a result of Pompeius' mastery over the water, he adopted the moniker Neptuni Filius, which means "son of Neptune". The embargo on Italy was removed after Augustus gave Pompeius Sardinia, Corsica, Sicily, and the Peloponnese and guaranteed him a future seat as consul for 35 BC with the Treaty of Misenum, which established a temporary peace pact.

Once Augustus divorced Scribonia and wed Livia on January 17, 38 BC, the triumvirate's agreement with Sextus Pompeius about the division of their territories started to fall apart. One of Pompeius' naval captains betrayed him by giving Octavian control of Corsica and Sardinia. However, because of the lack of resources for Augustus to take on Pompeius alone, a deal was made to extend the Second Triumvirate for a further five years beginning in 37 BC.

In Sicily in 36 BC, Augustus and Lepidus together launched an offensive against Sextus. At the naval Battle of Naulochus, Augustus was able to defeat Sextus Pompeius with little assistance from Lepidus and Antony. Later, one of Antony's generals killed Pompeius. Sextus had fled east with his remaining men.