The Emperor Aurelian did something to check the complete disintegration of the empire. In addition to capturing some enemies in the East he brought back Gaul, Britain and Spain into the empire. But it was he who abandoned Dacia and built around Rome the great wall, twelve feet thick and twenty high, of which you can still see large sections in the imperial city. But Aurelian was assassinated, and so there was another period of chaos until in 285 AD the Illyrian, Diocletion, gained control. Such is a brief sketch of the ordeal through which the Roman world passed in the one hundred and five years from the death of Marcus Aurelius to the accession of Diocletion.
Mere words can scarcely convey the agony through which the inhabitants of that world passed.
There was murder, rape, and pillage. What the soldiers or the barbarians spared, the agents of the emperors took for taxes. The old bureaucracy of senators and knights was pretty well exterminated. In its place came a military hegemony of soldiers who had risen from the ranks. Both the army which maw included many barbarians, and the senate were equalized and, in consequence, barbarized.