The Byzantine World War explains how the origins of the Crusades began with the collapse of the Byzantine Empire. The Byzantine Empire was a continuation of the Roman Empire – the eastern half that survived the fall of Rome itself. In the Middle Ages, it was confronted by an Islamic super-power, the Seljuk Turkish Sultanate, which stretched from India to the Mediterranean.
The Byzantine Empire was invaded by the Seljuk Turks in the mid-eleventh century. A ferocious war ultimately culminated in one of the greatest battles of the Middle Ages, the battle of Manzikert in 1071. The Byzantines were led by a heroic Emperor who might have defeated the Turks were it not for treachery on his own side.
Byzantine defeat led to the First Crusade which began as a popular movement in Western Europe to save Byzantium. Hundreds of thousands of knights, peasants, men and women, marched east to fight the Turks. Their success was breath-taking, matched only by the victories of Alexander the Great and Napoleon. They defeated Turkish, Arab and Egyptian armies and captured Jerusalem, which had been in Muslim hands for over four hundred years. Although it was a great victory for the West, the brutality of the conflict led to a seismic split between Christianity and Islam which is still with us today.