Rome and Iran fought for nearly seven centuries
From Crassus's disaster at Carrhae in 53 BC to the final Byzantine–Sasanian clash ending in 628 AD, Roman and Iranian empires traded border towns without lasting conquest. Their sixth- and seventh-century exhaustion then left both open to the sudden rise of the Rashidun armies.
The Roman–Persian or Roman–Iranian wars began between the Roman Republic and Parthia in 54 BC and closed when Byzantium and the Sasanian state finished fighting in 628 AD. Aside from northern adjustments, the frontier stayed broadly stable even as forts and provinces were sacked and swapped; neither side could hold deep conquests for long. James Howard-Johnston framed both as grand imperial players able to secure territories across regions from the third century BC into the early seventh century AD.
Parthian western policy revived under Mithridates II, who failed to seal an alliance with Sulla around 105 BC. Marcus Licinius Crassus invaded Mesopotamia in 53 BC and died with his son at Carrhae under Surena—Rome's worst reverse since Arausio. Parthians raided Syria afterward, stayed mostly neutral in Caesar's civil war while aiding Pompeians, and later struck a 1 AD compromise with Octavian that pulled Parthian forces from Armenia while recognizing a Roman protectorate there, though rivalry over Armenia continued for generations. In 114 and 115 Trajan annexed Armenia and Mesopotamia as provinces, took the Parthian capital Ctesiphon and sailed on to the Persian Gulf, yet Hadrian soon handed those gains back and fixed the Euphrates as Rome's limit. Avidius Cassius sacked Ctesiphon again in 165, but an epidemic, possibly smallpox, spread from Parthia to his troops and became the Antonine Plague.
Centuries of escalating sixth- and seventh-century warfare drained both empires' manpower and treasure. When Arab Muslim forces under the Rashidun Caliphate expanded, they met opponents already spent by mutual siege. The long duel thus shaped late antique geopolitics less by final victory than by shared exhaustion—an expensive stalemate that cleared the stage for a new power neither Rome nor Iran had trained to face across the desert frontiers.
Source: Roman–Persian wars
