Responding to the call of Pope Urban II at Claremont in 1095, the Christian knights of the First Crusade set out for the Holy Land. In 1099, Jerusalem was captured. As their port in Palestine, the Crusaders settled on Acre on the Mediterranean. There they built the great castle that was overrun by Saladin in 1187, but retaken by Richard the Lion-Hearted in 1191. Acre became the capital of the Kingdom of Jerusalem and the stronghold of the Crusader state, which fell to the Mameluks in a bloody siege in 1291. The Christians left behind were massacred. The ruins of...