In 1143 the deaths of both the Byzantine Emperor John and King Fulk of Jerusalem created a power vacuum in the Christian Middle East. Hemmed in by hostile Muslim states, Joscelin II, Count of Edessa, needed a Muslim ally; he chose the Artuqids, a Turkmen dynasty, and marched his army to join them in an attack on Aleppo, a stronghold of the rival warlord, Zangi. Zangi exploited Joscelin’s absence to lay siege to Edessa. Lacking the forces to take on Zangi, Joscelin retired to his fortress at Turbessel, and requested reinforcements from the Byzantines; the new Queen Regent, Melisende of Jerusalem, and Raymond of Antioch. None were willing or able to help. Inevitably, after a four-week siege, Edessa fell. It was the first crusader city to be reconquered, and its fall both revitalized the various Muslim powers in the Middle East and acted as catalyst for the Second Crusade.
— OR —