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.
Baldwin I of Jerusalem
Pope Urban II proclaimed the First Crusade at the Council of Clermont on 27November 1095. Godfrey of Bouillon decided to join the military campaign and sold or mortgaged his inherited domains to raise funds. One of his domains, the County of Verdun, was seized by Richer, Bishop of Verdun, who soon granted it to Baldwin. The dissolution of Godfrey's allodial lands deprived all future dukes of the basis of their authority in Lower Lotharingia, which facilitated Baldwin's decision to take the Cross. Eustace III of Boulogne also joined the crusade. According to a letter from Pope Urban, only the army that Peter the Hermit had mustered for the People's Crusade outnumbered the three brothers' force.