Legio XIII was levied by Julius Caesar in 57 BC, before marching against the Belgae, in one of his early interventions in intra-Gallic conflicts.

After the end of the Gallic wars, the Roman Senate refused Caesar his second consulship, ordered him to give up his commands, and demanded he return to Rome to face prosecution.

Forced to choose either the end of his political career or civil war, Caesar brought Legio XIII across the Rubicon river and into Italy.

After the disaster of the Battle of the Teutoburg Forest in AD 9, the legion was sent as reinforcements to Augusta Vindelicorum (Augsburg), and then to Vindonissa, Raetia, to prevent further attacks from the Germanic tribes.

Emperor Claudius sent them back to Pannonia around 45 and the legion built its legionary fortress at Poetovium (modern Ptuj, Slovenia).