Soon after returning form his 1908 cycle tour of French castles, Lawrence discussed his proposed thesis with C. F. Bell at the Ashmolean. Bell suggested that a much more interesting study could be written comparing the castles of medieval Europe to those of the Crusaders, in order to determine whether certain architectural features had their origins in Europe or the East. Lawrence was intrigued by the idea, which he could put into practice by changing his special paper from 'Military History and Strategy' to 'The first three Crusades'.

By the beginning of January 1909 he had decided to make a tour of the major crusader castles, few of which had been adequately planned or described. He intended to travel on foot, relying on the hospitality of local villagers; he therefore learned a little colloquial Arabic. Since there would be no picture postcards for sale he also took lessons in drawing from the architectural illustrator E. H. New.