In 1143 both John II and Fulk of Jerusalem died, leaving Joscelin II with no powerful allies to help defend Edessa. In autumn 1144, Joscelin II formed an alliance with the Artuqid Kara Aslan and marched a sizable army north to assist in their struggle with Zengi. With the capital only lightly defended, Zengi redirected his army, invading and capturing the city after the Siege of Edessa in 1144. Joscelin II fled to Turbessel, where he held the remnants of the county west of the Euphrates.