The traditional view is that the third century was one both of militarism and of urban decline. Modern historians, scarred by their own political experience in the first half of the twentieth century and a paucity of classical sources, viewed that period of the Roman empire pretty much entirely in negative terms. That view was backed up by archaeology of increasing fortification and burned layers.
Simon Esmonde Cleary's The Roman West, AD 200-500: An Archaeological Study. Cambridge; New York: Cambridge University Press, 2013, is a useful antidote to the "crisis of the third century" and provides a different perspective. Reviewed in BMCR:
Regarding Northern Gaul, Esmonde Cleary suggests that changes in the use of urban spaces from the late second century, such as the abandonment of fora and bathhouses, and the erection of defensive circuits, do not signal continual military crisis. Rather, he argues, they show a development in the kind of citizen the region was attempting to produce: under the high empire, the region could concentrate on producing citizens versed in the niceties of the Graeco-Roman lifestyle; under the progressive militarisation of the late second century onwards, their architectural focus adapted to the circumstances, adopting an increasingly militaristic flavour. The shift to militarisation was not absolute, and the 'function' of cities varied.
See full review by the University of Manchester's Steven Spiegl here.