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.
Christian forces of the First Crusade
Among the nobles whose affiliations are not known are: Charles I, Count of Flanders, who is said to have travelled with an armada in 1107 (see above);  Berengar Raymond II, Count of Barcelona, who took the cross as penance for the murder of his brother;  Bernard II, Count of Besalú, took the cross for the First Crusade but remained in Spain at the counseling of the pope;  Fernando Díaz, one of the few Spaniards to participate in the Crusades; and  Erard I, Count of Brienne, either went on the First Crusade or on a pilgrimage to the Holy Land in 1097.