Prior to the Crusades, you have to realize that the back and forth fight over the holy ground had gone on far before that. Islam took over much of what Christians and Jews considered Holy territory as well. The Roman Emperor, Constantine the Great (Roman Emperor who ended the persecution of Christians in Rome), created Constantinople (old Byzantium Empire) somewhere between 300 - 400 AD while Islam didn't necessarily begin until around 500-600 AD. The first Crusade was launched around 1100 AD. While the 'purpose' of this Crusade was to reclaim the Holy Lands for Christians, it was truly joined by the masses in hopes of re-opening the critical lifelines of trade that were lost at the fall of the Roman Empire. The fall of the Roman Empire cast of Western Europe into the Dark Ages in which Feudalism reigned and chaos insued.
