Byzantine–Sassanid wars

The Byzantine–Sassanid frontier in Late Antiquity

Date	285 to c. 628
Location	Caucasus, Asia Minor, Egypt, Levant, Balkans, Mesopotamia, Balkans, Aegean Sea
Result	Status quo ante bellum

Belligerents

Byzantine Empire

Sassanid Empire

Commanders and leaders

Justinian,
Belisarius,
Heraclius

Kavadh I,
Khosrau I,
Khosrau II,
Shahrbaraz,
Rhahzadh,
Shahin

The Byzantine–Sassanid wars, also known as the Irano-Byzantine wars refers to a series of conflicts between the Eastern Roman (Byzantine) Empire and the Sassanid dynasty of the Persian Empire. A continuation of the Roman–Persian Wars, the conflict involved several smaller campaigns and peace treaties lasting for years at a time.

The Roman Empire had reached its greatest extent under the Emperor Trajan. However, before Trajan, the Emperor Augustus set about stabilizing the frontiers of the Empire. As a result, the Romans were more interested in simply defending their territory and consolidating the Empire rather than in attempting to conquer Persia.

The Romans employed the best infantry of the time: heavily armed and armoured soldiers plus numerous auxiliaries. By the 4th century A.D., armour was less often used, and by the 5th century, Germanic mercenaries were employed. The Romans continued to use heavy infantry of the legionary type, but these were ineffective against the mobile Persian horse archers. From the 3rd century heavy cataphract cavalry wearing full horse and rider armour became an increasingly important component of Roman armies.

The Sassanid dynasty had a more or less secure northern and eastern border due to the mountainous terrain of the Caucasus, Middle Asia and Afghanistan. The Western border was determined by Sassanid control of Mesopotamia. Due to the flat nature of the land, it was easy to overrun and difficult to defend. With these natural boundaries, the Sassanid Persians had only Westward to expand. The Sassanids were becoming as efficient in siege warfare as the Romans, capturing and sacking a number of cities as part of a larger goal of exacting tribute and land from the Romans. However, the nature of the warfare was one of attrition with heavy casualties on both sides. As a result, little land was exchanged between the two powers; rather, vassal states and tribute would have been demanded.

The Sassanid Persians employed cavalry archers and heavy cataphracts to counter the heavy Roman infantry. In battle, these archers proved their worth until the Romans began to adopt similar methods of warfare.

Following Trajan's successful conquest of Mesopotamia in the 2nd century, the Parthian dynasty began to decline. Ctesiphon was overrun by the Romans but the lack of any permanent establishment meant that the Sassanid dynasty filled the power vacuum in the region and started a new Persian Empire in 224. The Sassanids were a more aggressive enemy than their Parthian predecessors and consequently, the Romans found themselves fighting a more dangerous Eastern opponent at a time when the Roman Empire was weakening due to the civil chaos arising from the death of the Roman Emperor Commodus.

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