Eastern Roman army
| Part of a series on the |
| Military of ancient Rome |
|---|
| Ancient Rome portal |
| Part of a series on the |
| Byzantine army |
|---|
| Structural history |
|
|
| Campaign history |
| Lists of wars, revolts and civil wars, and battles (Constantinople) |
| Strategy and tactics |
|
The Eastern Roman army refers to the army of the eastern section of the Roman Empire, from the empire's definitive split in 395 AD to the army's reorganization by themes after the permanent loss of Syria, Palestine and Egypt to the Arabs in the 7th century during the Byzantine-Arab Wars. The East Roman army was the continuation of the Late Roman army of the 4th century, until it gradually transformed into what is now called the Byzantine army from the 7th century onwards.
The East Roman army was a direct continuation of the eastern portion of the late Roman army as it existed before the final division of the empire. The East Roman army initially maintained the same basic organization as the late Roman army and its West Roman counterpart, but gradually underwent significant structural changes between the 5th and 7th centuries. Cavalry became more important, mobile field armies took on a more prominent role, and the border armies were eventually transformed into local militias.
In the 6th century, Emperor Justinian I, (r. 527–565 AD), sent much of the East Roman military to participate in the partial reconquest of several portions of the former Western Roman Empire. In these wars, the Eastern Roman Empire reconquered parts of North Africa from the Vandal Kingdom, most of Italy from the Ostrogothic Kingdom, and parts of southern Spain. The strength of the East Roman army diminished greatly during Justinian's reign, due in large part to the severe demographic impact of the Plague of Justinian on the population of the Eastern empire. In the 7th century, the East Roman army fought a long and destructive war against the Sasasian Empire under the leadership of Heraclius. Heraclius temporarily regained Egypt and Syria from the Sasanians, but almost immediately faced an invasion by the expanding Rashidun Caliphate. His generals’ defeat at the Battle of Yarmuk lead directly to the Islamic conquest of Syria and Egypt, and ultimately caused the reorganization of the East Roman army into the thematic system of later Byzantine armies.