But by the fourth century, the migrations started reaching alarming levels as the Germans began entering the empire in larger and larger numbers. To the Romans, the once peaceful settlers were rapidly becoming unwelcome and threatening invaders. The increase in migrations was due primarily to invasions that Germany was experiencing on its northern and eastern borders by marauding bands of Slavs and Huns. The Slavs and Huns, whose homelands were eastern Europe and north-central Asia, respectively, would eventually move as far west as Italy, threatening the city of Rome itself.

The empire mustered all of its strength and resources to stem the onslaught, but to little avail. There were fundamental problems undermining any chance of success. Rome was experiencing serious political and economic difficulties throughout most of the third and fourth centuries. Between the years 235 and 285, for example, the empire had a total of...