In the Hadrianople campaign in 377-382, and again in the Rhine crossing at the end of 406, the Roman Empire’s lower social orders had been willing to help or even join in with the barbarian invaders. Here we have early instances of the way in which outside military forces could open up pre-existing fault lines within the Roman political system. This is not surprising, given how little such groups had invested in the system run by and for the landowning classes. The willingness of the landowning elite to do deals with barbarians was a very different phenomenon—and much more dangerous for the Empire. But it, too, had its origins in the nature of the system. Given its vast size and limited bureaucratic technology, the Roman Empire could not but be a world of self-governing localities held together by a mixture of force and the political bargain that paying tax to the center would bring protection to the local landowning elites. The appearance of armed outside forces in the heart of the Roman world put that bargain under great strain. The speed with which some landowners rushed to support barbarian-sponsored regimes is not, as has sometimes been argued, a sign of lack of moral fiber among late Romans, so much as an indicator of the peculiar character of wealth when it comes in the form of land. In historical analysis, not to mention old wills, landed wealth is usually categorized in opposition to moveable goods, and that captures the essence of the problem. You cannot simply pick it up and move, as you would a sack of gold or diamonds, should conditions in your area change. If you do move on, you leave behind the source of your wealth, and all of your elite status. Landowners have little choice, therefore, but to try to come to terms with changing conditions, and this is what was beginning to happen around Rome in 408-410 and in southern Gaul in 414-415.

From Peter Heather’s The Fall of the Roman Empire: A New History, London: Pan Books, 2006 (first published in 2005), pp. 249-250.