Military history of the Crusader states
The Seljuk–Crusader War began when the First Crusade wrested territory from the Seljuk Turks during the Siege of Nicaea in 1097 and lasted until 1128 when Zengi became atabeg of Aleppo. At the latter date, the chief threat to the Crusaders from the east and north became the Zengids. The conflict was generally fought between European Crusaders and the Seljuk Turks and their vassals. The Muslim Syrian emirates occasionally allied themselves with the Christians against rival states.
History of the Middle East
Africa was reviving, however, as more organized and centralized states began to form in the later Middle Ages after the Renaissance of the 12th century. Motivated by religion and conquest, the kings of Europe launched a number of Crusades to try to roll back Muslim power and retake the Holy Land. The Crusades were unsuccessful but were far more effective in weakening the already tottering Byzantine Empire. They also rearranged the balance of power in the Muslim world as Egypt once again emerged as a major power.