 The Roman forts of Cumbria are "auxiliary forts" – that is, housing auxiliary units of infantry and cavalry, rather than a legion, as at Chester.So-called 'outpost-forts', with road links to the Wall, were built north of the Wall, probably at about the time the Wall itself was built in its turf and timber form.They include Bewcastle and Netherby in Cumbria, and Birrens in Dumfriesshire.