The new emperor, Diocletian, was faced with many problems

The Roman Empire had invaders at their borders, economic troubles, and unrest at home

In 285 A.D., Diocletian had a plan to divide the empire into two, East and West Roman Empires

Diocletian would rule the Eastern Roman Empire and his friend, Maximian, would rule the Western Roman Empire

They both appointed a junior emperor to help them rule (this new rule by four emperors was called a tetrarchy)

Each of these four emperors would focus on ruling a section to make it more manageable

They would cooperate to keep the Roman Empire alive and strong

The Tetrarchy raised the army's numbers to 400,000 soldiers

They reinforced the forces at the borders

They created a mobile force ready to report to trouble areas 

They broke the empire into manageable units 

Emperor worship and adherence to Latin was imposed

They made changes to their economy (taxes, currency, inflation, etc.)

Things went well for about 20 years

Maximian and Diocletian retired and the junior emperors took over (the best years of the Tetrarchy were over)

Constantine played a big role in Roman history: he fought to gain the seat to the empire after his emperor father died & made Christianity legal

The Tetrarchy denied Constantine the seat to the throne of the empire (become emperor)

Civil war occurs in Rome and Constantine wins

Constantine becomes emperor of the Western and Eastern Roman Empires

Constantine's interest in the Eastern Empire was more appealing

Rome in Italy had decreased in power and prestige

The Eastern Roman Empire had more people, food, taxes, and soldiers

The Western Roman Empire became weaker

Constantine moved the capital from Rome to Byzantium (a former Greek city)

He renames the city Constantinople

After his death, his sons took over but Eastern Rome fell into civil war

Theodosius (new emperor) reunited the Roman Empire

After Theodosius died in 395 A.D., the empire split into two, again (this time for good)