County of Edessa
The siege of Edessa (Arabic: "fatḥ al-Ruhāʾ", liberation of Edessa) took place from November 28 to December 24, 1144, resulting in the fall of the capital of the crusader County of Edessa to Zengi, the atabeg of Mosul and Aleppo. This event was the catalyst for the Second Crusade.