The document discusses the history of the Crusades between the 11th and 13th centuries. It began when Pope Urban II called for the First Crusade in 1095 to retake Jerusalem from Seljuk Turks and protect Christian pilgrims. This led to the establishment of Crusader states in the Holy Land. Subsequent crusades aimed to defend or retake lands but faced challenges from Saladin and failed to achieve lasting control over Jerusalem and the region. The Crusades had lasting religious, political, and economic impacts on relations between Christianity and Islam.