Legio X Fretensis was levied in 40-41 BC, by Julius Caesar’s heir, Octavian (who was later to become Emperor Augustus) during the civil war against Sextus Pompeius who was occupying Sicily and threatening the grain supply to Rome.
The “X” (number 10) was given as a reminder of another famous 10th legion which had served under Julius Caesar (although remnants of the old legion continued serving under Marc Anthony – Octavian’s rival).
The name “Fretensis” meant: “of the sea straits”. This came from the fact that the legion’s first role was as a naval infantry force guarding the Straits of Messina, (in those days known as the “Fretum Siculum”) the sea passage between Sicily and the Italian mainland peninsula. The legion received its combat baptism in the same area during 36 BC at the naval battle of Naulochus were Octavian’s ships achieved victory.
After this battle, Legio X Fretensis was stationed at Mylae, Sicily. With Sextus Pompeius defeated, a war between Octavian and Marc Anthony followed. The next major battle in which the Legion is found taking part, was in Actium, 31 BC, another naval conflict near the Western coast of Greece, which left Octavian victorious upon the forces of rival Marc Anthony and Egyptian Queen Cleopatra, allowing him supremacy rule and a paved way to become the first Roman Emperor.
A year later the legion moved location again to serve in the Macedonia region and remained there for several years.