 Withdrawing some legionaries from the fixed bases on the border, Gallienus created mobile forces (the "Comitatenses" or field armies) and stationed them behind and at some distance from the borders as a strategic reserve.The border troops ("limitanei") stationed at fixed bases continued to be the first line of defense.The basic unit of the field army was the "regiment", "legiones" or "auxilia" for infantry and "vexillationes" for cavalry.