Under Constantine the Great two great changes took place—the introduction of Christianity as the religion of the State, and the transference of the seat of government from Rome to Byzantium (A. D. 330), which was re-named after the emperor, Constantinople.
Persia at this time, under the Sassanian dynasty, attained a height of prosperity and power such as it had never before reached, and against it even the veteran Roman legions could gain no lasting laurels.
ABOUT A.D. 500
ABOUT A.D. 800
ABOUT A.D. 1000
