The Roman Empire was too large to be ruled by one man in one place, except in
peacetime. This became clear during the “crisis of the third century,” when two
different groups from two different directions bore down on the frontiers of the
Empire. From the north, beyond the Rhine and Danube rivers, came people the
Romans called “barbarians”; from the east came the Persians. To contend with these
attacks, the Roman government responded with wide-ranging reforms that brought
new prominence to the provinces.
Above all, the government expanded the army, setting up new crack mobile
forces while reinforcing the standing army. Soldier-workers set up new fortifications,
cities ringed themselves with walls, farms gained lookout towers and fences. It was
not easy to find enough recruits to man this newly expanded defensive system.
Before the crisis, the legions had been largely self-perpetuating. Their soldiers, drawn
mainly from local provincial families, had settled permanently along the borders and
raised the sons who would make up the next generation of recruits. Now, however,
this supply was dwindling: the birthrate was declining, and c.252–267 an epidemic of
smallpox ravaged the population further. Recruits would have to come from farther
away, from Germania (the region beyond the northern borders of the Empire) and
elsewhere. In fact, long before this time, Germanic warriors had been regular
members of Roman army units; they had done their stints and gone home. But in the
third century the Roman government reorganized the process. They settled Germanic
and other barbarian groups within the Empire, giving them land in return for military
service.
The term “crisis of the third century” refers not only to the wars that the Empire
had to fight on its borders, but also to a political succession crisis that saw more than
twenty men claim, then lose with their lives, the title of emperor between the years
235 and 284. (See list on p. 335: Late Roman Emperors; but note that this list names
only the most important emperors!) Most of these men were creatures of the army,
chosen to rule by their troops. Competing emperors often wielded authority in
different regions at the same time. They had little interest in the city of Rome, which,
in any case, was too far from any of the fields of war to serve as military
headquarters. For this reason Emperor Maximian (r.286–305) turned Milan into a
new capital city, complete with an imperial palace, baths, walls, and circus. Soon
other favored cities—Trier, Sardica, Nicomedia, and, eventually, Constantinople—
joined Milan in overshadowing Rome. The new army and the new imperial seats
belonged to the provinces.
The primacy of the provinces was further enhanced by the need to feed and
