Aurelian's campaign against the Persians was called off in 276 AD,
only a year later, after the deaths of two more emperors in the
field, as well as Persia's King Sapor. Rome continuously battled
against invading barbarians, and another campaign was led into
Mesopotamia in 283 AD. However, after a number of victories and the
death of another emperor leading the troops while away from Rome, it
too was ended. 284 AD saw the death of two more emperors, as well as
the ascension of Diocletian, an important figure in Roman history.
Although the empire's size had always dictated that it be truly ruled
not by one man, but by several regional administrators instead,
Diocletian began a system of dividing up the empire into sections,
each of which with it's own Augustus or Caesar. In 286 AD Diocletian
split the empire into east and west, sharing the title of Augustus
with Maximian in the west. Then in 292 AD he appointed two Caesars,
or deputy emperors, for the Danube region as well as Britain, Gaul
and Spain. However, Diocletian's system would run into problems soon
after his abdication in 305 AD and eventual death in 311 AD.
By 308 AD personal ambition had corrupted the dual Augustus system,
as six men proclaimed themselves emperor at once. Open war broke out
between the competitors in 314 AD. The problem was not solved until
around 325 AD with the defeat and execution of the fifth and final
rival of Flavius Valerius Constantinus, who became sole emperor.
Constantine was the first emperor of the Christian religion, and set
about making it the primary religion of his new empire. In 330 AD he
moved the capital of the empire from Rome to Byzantium, which he
renamed Constantinopolis (Constantinople). This ensured his new
Byzantine Empire would survive the loss of the western lands to the
aggressive barbarians, as well as adopting the styles and methods of
the east. Pagans and Jews were persecuted in favor of the Christians,
and grand architectural marvels were created in honor of both the new
empire and the new religious age. Constantine died in 337 AD,
although Constantinople and the Eastern Roman Empire would live on
until 1453, finally suffering defeat at the hands of the Ottoman Turks.