<P> Though the Empire had seen periods with more than one Emperor ruling jointly before , the view that it was impossible for a single emperor to govern the entire Empire was established by Emperor Diocletian following the disastrous civil wars and disintegrations of the Crisis of the 3rd century . His ideas were instituted in Roman law by the introduction of the Tetrarchy in AD 286 , which divided the position of Augustus ( Emperor ) into two ; one in the East and one in the West , each with an appointed Caesar ( junior Emperor and designated successor ) . Though the tetrarchic system would collapse in a matter of years , the East - West administrative division would endure in one form or another for centuries to come . As such , the Western Roman Empire would exist intermittently in several periods between the 3rd and 5th centuries . Though some emperors , such as Constantine I and Theodosius I , would manage to rise to the position of Augustus in both parts and as such reunify the Empire , it would often divide again upon their deaths . After the death of Theodosius I in AD 395 , the Empire was divided between his sons and would not be reunified . Eighty - five years later , in 480 , following various invasions and the collapse of central control in the West , Emperor Zeno of the Eastern Empire recognized the reality of the Western Empire 's reduced domain . Effective central control had ceased to exist even in the Italian Peninsula after the depositions of Julius Nepos and Romulus Augustulus -- and Zeno therefore abolished the Western court and proclaimed himself the sole emperor of the Roman Empire . </P>
<P> Though the Empire had seen periods with more than one Emperor ruling jointly before , the view that it was impossible for a single emperor to govern the entire Empire was established by Emperor Diocletian following the disastrous civil wars and disintegrations of the Crisis of the 3rd century . His ideas were instituted in Roman law by the introduction of the Tetrarchy in AD 286 , which divided the position of Augustus ( Emperor ) into two ; one in the East and one in the West , each with an appointed Caesar ( junior Emperor and designated successor ) . Though the tetrarchic system would collapse in a matter of years , the East - West administrative division would endure in one form or another for centuries to come . As such , the Western Roman Empire would exist intermittently in several periods between the 3rd and 5th centuries . Though some emperors , such as Constantine I and Theodosius I , would manage to rise to the position of Augustus in both parts and as such reunify the Empire , it would often divide again upon their deaths . After the death of Theodosius I in AD 395 , the Empire was divided between his sons and would not be reunified . Eighty - five years later , in 480 , following various invasions and the collapse of central control in the West , Emperor Zeno of the Eastern Empire recognized the reality of the Western Empire 's reduced domain . Effective central control had ceased to exist even in the Italian Peninsula after the depositions of Julius Nepos and Romulus Augustulus -- and Zeno therefore abolished the Western court and proclaimed himself the sole emperor of the Roman Empire . </P>
when did eastern and western roman empire split
when did eastern and western roman empire split
AD 286
AD 286