It is a matter of debate when the Roman Empire officially ended and transformed
into the Byzantine Empire. Most scholars accept that it did not happen at one time, but
that it was a slow process, and so late Roman history overlaps with early Byzantine
history.
Constantine I (“the Great”) is usually held to be the founder of the Byzantine
Empire. He was responsible for two major changes that would help create a Byzantine
culture distinct from the Roman past. First, he legalized Christianity, which had
previously been persecuted in the Roman Empire. He converted to Christianity, and
sponsored the Christian Church. Christianity would be a major feature at the heart of
Byzantine culture. The second major step taken by Constantine was moving the capital
of the Roman Empire to the city of Byzantium (the origin of the word “Byzantine”), which
he refounded as the city of Constantinople (it was also sometimes called “New Rome”).
Constantine’s founding of Constantinople in 330 AD is usually considered the beginning
of the Byzantine Empire. By moving the capital of the empire outside Italy and to the
East, Constantine moved the center of gravity in the empire to this region, right on the
divide between Europe and Asia Minor.
After Constantine, few emperors ruled the entire Roman Empire. It was too big,
and under attack from too many directions. Usually, there was an emperor of the
Western Roman Empire ruling from Italy or Gaul, and an emperor of the Eastern Roman
Empire ruling from Constantinople. While the Western Empire was overrun by
Germanic barbarians the Eastern Empire thrived, and Constantinople became the
largest city in the empire and a major commercial center.
In 476 AD, the last Western Roman Emperor was deposed and the Western
Roman Empire was no more. Its lands in Italy were conquered by the Ostrogoths,
Spain was conquered by the Visigoths, North Africa was conquered by the Vandals, and
Gaul was conquered by the Franks. This left the Eastern Roman Empire as the only
Roman Empire standing.
