Augustus probably sent his new XXIst legion to Hispania Tarraconensis to fight the campaign against the Cantabrians. XXI "Rapax" was one of the five legions used by Drusus to suppress the rebellion of the Raetians, in 16–15 BC. From 15 BC, the legion was stationed in "Castra Regina" (Regensburg), in the new province of Raetia.