Crusader castle in Syria

The announced purposes of the crusades were to relieve the eastern empire from the threat of Turkish invasion and to place the Holy Land under Christian control. Jerusalem was captured as early as 1099 and a number of Latin states were established in Palestine and Syria. Neither Jerusalem nor these states were permanently held. The crusades occasionally exacerbated relations between the eastern and western churches, particularly during the fourth crusade when western crusaders occupied Constantinople and there proclaimed a short-lived Latin empire. The last of the crusades occurred in the fifteenth century.