Freed from immediate external threats in the Balkans or in Anatolia, having defeated the Hungarians in 1129, and having forced the Anatolian Turks on the defensive, the Byzantine emperor John II Komnenos could direct his attention to the Levant, where he sought to reinforce Byzantium's claims to suzerainty over the Crusader States and to assert his rights and authority over Antioch.

Control of Cilicia opened the route to the Principality of Antioch for the Byzantines. Faced with the approach of the formidable Byzantine army, Raymond of Poitiers, prince of Antioch, and Joscelin II, count of Edessa, hastened to acknowledge the Emperor's overlordship. John demanded the unconditional surrender of Antioch and, after asking the permission of Fulk, King of Jerusalem, Raymond of Poitiers agreed to surrender the city to John.

The siege of Shaizar took place from April 28 to May 21, 1138. The allied forces of the Byzantine Empire, Principality of Antioch and County of Edessa invaded Muslim Syria. Having been repulsed from their main objective, the city of Aleppo, the combined Christian armies took a number of fortified settlements by assault and finally besieged Shaizar, the capital of the Munqidhite Emirate. The siege captured the city, but failed to take the citadel; it resulted in the Emir of Shaizar paying an indemnity and becoming the vassal of the Byzantine emperor. The forces of Zengi, the greatest Muslim prince of the region, skirmished with the allied army but it was too strong for them to risk battle. The campaign underlined the limited nature of Byzantine suzerainty over the northern Crusader states and the lack of common purpose between the Latin princes and the Byzantine emperor.