Battle of Edessa
260 CE.
Shown on the map at 37.150°, 38.800°.
The Battle of Edessa took place between the armies of the Roman Empire, under the command of Emperor Valerian, and the Sasanian Empire under Shapur I, in Edessa (now the Turkish city of Urfa) in 260. The Roman army was defeated and captured in its entirety by the Sasanian forces; for the first time, a Roman emperor was taken prisoner.
Text from the Wikipedia article Battle of Edessa, licensed CC BY-SA 4.0.