• The arrival of the Seljuk Turks
• A cry for help
• A Letter from Alexius
• Other origins of the Crusades
• Religious hysteria
• The rise of papal power
• The economics of the Crusades
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The Crusades did not happen spontaneously or as a result of a particular event. A number of factors came together to create the political, social, religious, and economic environment that enabled the "crusading spirit" to take root and spread throughout Europe. Although enthusiasm for crusading periodically cooled, it also revived in response to events in the Middle East.