Siege of Nisibis (237)

In 224 AD, Ardashir defeated the Parthian Empire and replaced it with the Sasanian Empire. He began to raid Roman territory almost immediately after he had taken power at Ctesiphon. When Severus Alexander launched a massive invasion of the Persian Empire in the early 230s, the Persian forces drove it back inflicting heavy casualties on the Roman army.A Companion to the Roman Empire "Ardashir began to raid the Roman territory almost immediately after he had taken power at Ctesiphon, making Roman armies look plodding and inept. When Alexander launched a massive invasion of his territory in the early 230s, Ardashir drove it back, inflicting heavy casualties. The Sasanians then besieged the Roman city of Nisibis in 235 or 237 and eventually conquered it.

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