Things you should know:
The Turks and the First Crusade
The modern nation of Turkey is named for its Turkish inhabitants, but the Turks were not originally from Turkey. The Turks were nomadic people from Central Asia. Many Turks remain in that area, in fact, there is a nation in Central Asia known as Turkmenistan (“land of the Turks”).
One Turkish tribe, the Seljuks, began moving into the Anatolian peninsula, or what we now call Turkey. These Turks were Muslims, and a Christian emperor, Alexius I, controlled the peninsula. Alexius appealed to the Pope to help him rid Anatolia of “the unbelievers.”
Pope Urban II received Alexius’s call for assistance, but decided to use that call to advance a more ambitious plan. Jerusalem, on the east coast of the Mediterranean Sea in the modern nation of Israel, is considered holy land to Christians, Jews and Muslims, but in 1095, the city was controlled by Muslims. The message from Alexius presented Urban with an opportunity to retake the holy lands from the Muslims. The pope called for a “War of the Cross,” or Crusade, to retake the holy lands from the unbelievers.
Pope Urban persuaded the knights of Europe to join the Crusades
Dowling, Mike. "The Crusades at mrdowling.com." www.mrdowling.com. Updated August 2, 2014 . Web. Date of Access. <http://www.mrdowling.com/606islam.html>