The Arabs captured Caesarea from the Byzantines in a.d. 639 and the Crusaders conquered the Arabs in 1101, discovering a green crystal vessel which they claimed to be the Holy Grail, the cup from which Jesus and his disciples drank during the Last Supper (it now reposes in Genoa).
The Arabs were conquered by the Crusaders during the 12th century. 
mnli hypothesis: The Arabs were conquered by the Crusaders during the 12th century.  premise: The Arabs captured Caesarea from the Byzantines in a.d. 639 and the Crusaders conquered the Arabs in 1101, discovering a green crystal vessel which they claimed to be the Holy Grail, the cup from which Jesus and his disciples drank during the Last Supper (it now reposes in Genoa).