Monumental documentary on the crusades produced by the History Channel entitled "Crusades: crescent and the cross".
The Crusades were a series of religious wars, blessed by the Pope and the Catholic Church with the main goal of restoring Christian access to the holy places in and near Jerusalem. The Crusades were originally launched in response to a call from the leaders of the Byzantine Empire for help to fight Muslim Seljuk Turks expansion into Anatolia; these Turks had cut off access to Jerusalem. The crusaders comprised military units from all over western Europe, and were not under unified command. The main series of Crusades occurred between 1095 and 1291; historians have given them numbers, later unnumbered crusades were also taken up for a variety of reasons. The Crusades were fought by Roman Catholics primarily against Muslims. After some early successes, the later crusades failed and the crusaders were defeated and forced to return home.
Several hundred thousand soldiers became Crusaders by taking vows, the Pope granted them plenary indulgence. Their emblem was the cross--"crusade" is derived from the French term for taking up the cross. Many were from France and called themselves "Franks," which became the common term used by Muslims.
The term "crusade" is also used to describe religiously motivated campaigns conducted between 1100 and 1600 in territories outside the Levant usually against pagans, heretics, and peoples under the ban of excommunication for a mixture of religious, economic, and political reasons. Rivalries among both Christian and Muslim powers led also to alliances between religious factions against their opponents, such as the Christian alliance with the Sultanate of Rûm during the Fifth Crusade.
The Crusades had major far-reaching political, economic, and social impacts on western Europe, and as well ruined the Byzantine Empire.
The Reconquista, a long period of wars in Spain (Iberia) where Christian forces reconquered the peninsula from Muslims, is closely tied to the Crusades.