Legio X Fretensis ("Tenth legion of the Strait") was a legion of the Imperial Roman army. It was founded by the young Gaius Octavius (later to become Augustus Caesar) in 41/40 BC to fight during the period of civil war that started the dissolution of the Roman Republic. X Fretensis is then recorded to have existed at least until the 410s. X Fretensis symbols were the bull — the holy animal of the goddess Venus (mythical ancestor of the gens Julia) — a ship (probably a reference to the Battles of Naulochus and/or Actium), the god Neptune, and a boar. The symbol of Taurus may also mean that it was organized between 20 April and 20 May. History Aelius Gallus' expedition In 26 BC, the Legio under Aelius Gallus was ordered by Augustus to undertake a military expedition to Arabia Felix, where Gallus was to either conclude treaties making the Arabian people foederati (i.e. client states), or to subdue them if they resisted. According to Theodor Mommsen, Aelius Gallus sailed with 10,000 legionaries from Egypt and landed at Leuce Kome, a trading port of the Nabateans in the northwestern Arabian coast. Gallus' subsequent movements relied on a Nabataean guide called Syllaeus, who proved to be untrustworthy. As a result of Syllaeus' misdirections, the army took six months to reach Mariba, the Sabaean capital. They besieged Ma'rib unsuccessfully for a week, before being forced to withdraw. Mommsen ascribed this to a combination of disease, over-extended supply lines, and a tougher desert environment than the Romans had expected. Gallus' retreat to Alexandria was completed in sixty days. Details of the expedition to Arabia Felix are given by Strabo, Cassius Dio and Pliny the Elder. Strabo's account is particularly detailed, and derives most of its information from Aelius Gallus himself, who was a personal friend of Strabo. The campaign is the subject of a 1951 novel, The Eagle and the Sun by Lord Belhaven, who had done military and civilian service in the region. Civil wars of the Republic and early Empire Octavian, later known as Augustus, levied a legion and gave it the number ten, as a reference to Julius Caesar's famous Tenth Legion. In 36 BC, the Tenth Legion fought under Octavian against Sextus Pompey in the Battle of Naulochus, where it earned its cognomen Fretensis. The name refers to the fact that the battle took place near the sea Strait