Pope Urban II ordered the First Crusade in 1095. This crusade was initially in response to the plea for aid from the Byzantine emperor as he sought to fight off invading Seljuk Turks, but the crusade eventually focused on taking Jerusalem and the Holy Land from Muslim hands. In 1099, Jerusalem fell to Christian armies. These armies slaughtered almost all of the Jews and Muslims in the city and subsequently established the Kingdom of Jerusalem.

SEED: The crusade's initial purpose evolving into a holy war of conquest is a rich angle for an essay on how stated motivations obscure actual objectives.

Green, Todd H, The Fear of Islam_ An Intro…, loc. 110