Provinces · The later western provinces
LW-26 Britannia Secunda

The name distinguished one of the late civil jurisdictions from its neighbours, but did not simply preserve Britannia Inferior unchanged. Civil subdivision and military command followed different practical requirements. Frontier armies, roads, towns, rural producers, and supply networks therefore cannot all be assigned by the provincial name alone.
The north’s military importance continued through fourth-century recovery and renewed insecurity. In the early fifth century, weakening imperial support transformed its institutions. Later northern kingdoms and communities arose from a complex regional world whose Roman inheritance included forts, towns, Christianity, and military traditions, without preserving a demonstrable exact provincial border.