The period known as the Crusades, a series of religiously motivated military expeditions originally intended to bring the Levant back into Christian rule, began. Several Crusader states were founded in the eastern Mediterranean. These were all short-lived. The Crusaders would have a profound impact on many parts of Europe. Their Sack of Constantinople in 1204 brought an abrupt end to the Byzantine Empire. Though it would later be re-established, it would never recover its former glory. The Crusaders would establish trade routes that would develop into the Silk Road and open the way for the merchant republics of Genoa and Venice to become major economic powers. The Reconquista, a related movement, worked to reconquer Iberia for Christendom.

What is the name of the period of armed incursions undertaken in the name of Christianity?