 The raids by the Picts and Scots in the late 4th and early 5th centuries (the so-called 'Pictish Wars'), meant increasing strain.For example, between 385 and 398 (when Stilicho cleared the raiders out), Cumbria was 'left to its own devices'.The various phases of re-modelling of the Birdoswald fort in the second half of the 4th century suggest that it was becoming more like a local warlord's fortress than a typical Roman fort.