Crusades, military expeditions, beginning in the late 11th century, that were organized by western European Christians in response to centuries of Muslim wars of expansion. Their objectives were to check the spread of Islam, to retake control of the Holy Land in the eastern Mediterranean, to conquer pagan areas, and to recapture formerly Christian territories; they were seen by many of their participants as a means of redemption and expiation for sins. Between 1095, when the First Crusade was launched, and 1291, when the Latin Christians were finally expelled from their kingdom in Syria, there were numerous expeditions to the Holy Land, to Spain, and even to the Baltic; the Crusades continued for several centuries after 1291. Crusading declined rapidly during the 16th century with the advent of the Protestant Reformation and the decline of papal authority.
Approximately two-thirds of the ancient Christian world had been conquered by Muslims by the end of the 11th century, including the important regions of Palestine, Syria, Egypt, and Anatolia. The Crusades, attempting to check this advance, initially enjoyed success, founding a Christian state in Palestine and Syria, but the continued growth of Islamic states ultimately reversed those gains. By the 14th century the Ottoman Turks had established themselves in the Balkans and would penetrate deeper into Europe despite repeated efforts to repulse them.
The Crusades constitute a controversial chapter in the history of Christianity, and their excesses have been the subject of centuries of historiography. The Crusades also played an integral role in the expansion of medieval Europe.
