How were the Crusades a turning point in Western history?

The Crusades were a series of religious military campaigns taking place between the 11th and 13th centuries. After Islamic Turks defeated the forces of the Byzantine Empire and conquered the Christian Holy Lands, including Jerusalem and Palestine, the Christian church and Pope Urban II called for a European uprising to return the Holy Lands to Christian control. This resulted in many bloody and brutal battles, not only against Muslims, but also against Jews, other Christians, and anyone else who would stand in the way of the crusaders.

The Crusades, though never achieving the original goal of returning the Holy Lands to Christian control, is still considered a major turning point in Western history because of its long-lasting effects on Europe, the Middle East, as well as on the Christian and Muslim worlds. For example, the crusaders of the Fourth Crusade sacked the Christian city of Constantinople, which in effect made permanent the divisions between the Roman Catholic and Eastern Orthodox churches. But more significantly, the Crusades taught the Western world to reach beyond Europe in their attempts at conquest, with a particularly new emphasis on the use of military power to achieve its goals.

But the impact on the Middle East and the Muslim world is perhaps the most significant and devastating, because the Crusades are seen as the first real attempt by the Roman Catholic Church to fight the expansion of Islam, which in turn has shaped modern Muslim viewpoints of the West. In fact, the term crusade is still used, in a negative way, to describe the continued involvement of the West in Middle Eastern affairs.