This legion was probably created to deal with Sextus Pompeius, the last opponent of the Second Triumvirate, garrisoned in Sicily and threatening Rome's grain supply.
[citation needed] Following the defeat of Antony and Cleopatra in the battle of Actium (31 BC), the legion was stationed in Gaul.
In the end of the 1st century BC, the XVIIIth was sent to the Germania provinces in the Rhine to take part in the enormous army led by Drusus and later Tiberius.
On September 9, Arminius, leader of the Cheruscan allies, reported a rebellion in the Rhine area.
Without suspecting the information received, Varus took his three legions, the XVIII along with XVII and XIX, and headed west.