Whereas the Middle Roman Period is marked by the Pax Romana (a time of relative prosperity and peace for the empire), the Crisis of the Third Century (c. 235-284 CE) witnessed a series of catastrophes, including barbarian invasion, plague, civil war and economic depression. At the peak of the Crisis, between 268 and 275 CE, the empire had briefly split into three competing states – the Gallic Empire; the Palmyrene Empire; and the Italian-centred Roman Empire. By the time the Crisis ended with Emperor Diocletian's ascension and creation of the Tetrarchy in 284 CE, the economic and physical damage to previously thriving cities was irreversible.
Due to constant warfare, a breakdown in thriving trading networks and the debasement of the currency, many Roman settlements were abandoned as populations dispersed to safer and more stable locales. For those cities and towns that remained, they rebuilt but this time with thick fortification walls.
Tongeren’s relative size and importance means it was never abandoned as a result of the Crisis. However, archaeological evidence shows a gap in occupation in and around Maastricht between the late third and early fourth centuries. This abandonment coincides with a distinctive break in Maastricht’s construction, function and operations — both in the small urban settlement and the wider rural landscape.