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.
Crusades
Both Philip I of France and Emperor HenryIV were in conflict with Urban and declined to participate in the official crusade. However, members of the high aristocracy from France, western Germany, the Low countries, and Italy were drawn to the venture, commanding their own military contingents in loose, fluid arrangements based on bonds of lordship, family, ethnicity, and language. Foremost amongst these was the elder statesman, Raymond IV, Count of Toulouse. He was rivalled by the relatively poor but martial Bohemond of Taranto and his nephew Tancred from the Norman community of southern Italy. They were joined by Godfrey of Bouillon and his brother Baldwin I of Jerusalem in leading a loose conglomerate from Lorraine, Lotharingia, and Germany. These five princes were pivotal to the campaign that was also joined by a Northern French army led by Robert Curthose, Stephen, Count of Blois, and Robert II, Count of Flanders. The armies, which may have contained as many as 100,000 people, including non-combatants, travelled eastward by land to Byzantium where they were cautiously welcomed by the Emperor. Alexios persuaded many of the princes to pledge allegiance to him and that their first objective should be Nicaea, which Kilij Arslan I had declared the capital of the Sultanate of Rum. Having already destroyed the earlier People's Crusade, the over-confident Sultan left the city to resolve a territorial dispute, enabling its capture in 1097 after a Crusader siege and a Byzantine naval assault. This marked a high point in Latin and Greek co-operation and also the start of Crusader attempts to take advantage of political and religious disunity in the Muslim world: Crusader envoys were sent to Egypt seeking an alliance.