 They were therefore largely less well armed and less well trained than "auxilia" or legions, although more prestigious elite irregular native troops were also utilised.However, the legions still made up around one half of the Roman army at this point.By the late Empire, enemy forces in both the East and West were "sufficiently mobile and sufficiently strong to pierce [the Roman] defensive perimeter on any selected axis of penetration"; from the 3rd century onwards, both Germanic tribes and Persian armies pierced the frontiers of the Roman Empire.