What caused the Byzantine-Sasanian conflicts under Justinian?

During the reign of Justinian, the Byzantine Empire and the Sasanian Empire fought major conflicts like the Iberian War and the Lazic War over strategic client states and trade routes. These protracted struggles eventually led to peace treaties involving financial tribute, setting the stage for centuries of exhausting rivalry between the two powers. Ultimately, this sustained military exhaustion left both empires vulnerable to the early Muslim conquests.

What we know

• The Iberian War was fought from 526 to 532 between the Byzantine and Sasanian empires over the eastern Georgian kingdom of Iberia after it defected to the Byzantines. [1, 2]
• The conflict between the Byzantines and Sasanians was fueled by tensions over tribute and the spice trade. [2]
• The Lazic War lasted for twenty years from 541 to 562 and concluded with a peace treaty requiring the Byzantine Empire to pay annual tribute to Persia for recognition of Lazica as a Byzantine vassal state. [4]
• The prolonged warfare and resource exhaustion during the 6th and 7th-century conflicts left both empires military exhausted and vulnerable to the Rashidun Caliphate. [3, 5]

Where to go next

• a case in pointHow did the Lazic War unfold over its twenty years?
• whenWhat was the Perpetual Peace of 532?
• the bigger pictureHow did the Roman-Persian wars span seven centuries?
• how it workedWhat role did vassal kingdoms play as proxies in these wars?
• what followedHow did the Last Great War of Antiquity begin?
• an unexpected connectionHow did ancient border conflicts lead to the rise of the Rashidun Caliphate?The centuries-long military exhaustion between the Byzantine and Sasanian empires directly enabled the rapid expansion of the Rashidun army into both weakened territories.

Sources

• [1]Iberian War (Wikidata Q2326066) · CC0 1.0
• [2]Iberian War · CC BY-SA 4.0
• [3]Roman–Persian wars · CC BY-SA 4.0
• [4]Lazic War · CC BY-SA 4.0
• [5]Byzantine–Sasanian War of 602–628 · CC BY-SA 4.0