This Legion was formed by Julius Caesar in Gaul in 57 BC, just before he attacked the Belgains. It served under him with distinction throughout the Gallic Campaigns, including against the Nervians, Aremoricans, at Gergovia and the Siege of Alesia. When Caesar crossed the Rubicon in 49, this was the Legion with which, as Livy said, Caesar "assailed the world". After the decisive Battle of Pharsalus in 48, the soldiers were sent back to Italy to be given their pensions and land, but in 46, it would again fight under Caesar in his African Campaign. After the Battle of Munda in 45, the troops were disbanded and given land at Spello, in Italy. When a new 13th Legion was formed in 41, this was not a new unit but a reconsitution of Caesar's 13th. On at least one occasion, the men of the Legion saved Octavian's life. After Octavian's victory at the Battle of Actium in 31, the Legion was reinforced with soldiers from disbanded units, which was when it was given its permanent surname, 'Twin'. It was afterwards stationed in both Illyricum and Gaul. It aided Augustus' son-in-law Tiberius when he conquered the Alpine regions. In 6 AD, it fought against the Marcomanni, and afterwards in the Balkans. After the Teutoburg Forest disaster in 9, it would defend strategic crossing points through the Alps against a possible Germanic invasion. After serving in various civil conflicts amongst Roman Emperors, the Legion fought against the rebel Batavians in 70, and under Domitian in his campaigns against the Suebians and Sarmatians. After Trajan's Dacian conquests, the 13th was seen as the most important unit in those newly-won regions. During Commodus' reign, it aided in defeating the Sarmatians, and between 180-244 AD, commanders of the Legion would erect no less than seventeen major altars. After Dacia's evacuation, the Legion was stationed at Ratiaria (northern Bulgaria), where it remained until the early 5th century. Although most Caesarian units used a bull emblem, the 13th was known to use a lion, which was the symbol for 'Twin'.