The Crusades: The siege of Shaizar ended, and the Emir of Shaizar became a vassal of the Byzantine Empire.

The Crusades were a series of religious wars initiated, supported, and at times directed by the Papacy during the Middle Ages. The most prominent of these were the campaigns to the Holy Land aimed at reclaiming Jerusalem and its surrounding territories from Muslim rule. Beginning with the First Crusade, which culminated in the capture of Jerusalem in 1099, these expeditions spanned centuries and became a central aspect of European political, religious, and military history.

The city of Shaizar was besieged 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.

The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived the events that caused the fall of the Western Roman Empire in the 5th century AD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'.