It's the Age of Faith

The Holy Roman Empire is 

the strongest kingdom in Europe

The Church has considerable 

spiritual and political power

Over 500 massive Gothic cathedrals 

(Cities of God) are built throughout 

Europe between 1170 and 1270

Jerusalem

In the late eleventh century, Jerusalem was controlled by the Muslims

It was Islam's 3rd holiest City (after Mecca & Medina)

It's the Holy City to Jews

and ... it's a Holy City to Christians

The "Holy War"

Pope Urban II put out the call for Christians to recapture Jerusalem and the Holy Land from Muslim Turks

Thus began 200 years of religiously sanctioned military campaigns, from 1095 to 1291

crusade means "taking of the cross" (crux)