Siege of Edessa
1144 CE.
Shown on the map at 37.150°, 38.800°.
The siege of Edessa took place from 28 November to 24 December 1144, resulting in the fall of the capital of the County of Edessa to Imad al-Din Zengi, the atabeg of Mosul and Aleppo. This event was the catalyst for the Second Crusade.
Text from the Wikipedia article Siege of Edessa (1144), licensed CC BY-SA 4.0.