marco polo mentions that one of the "princes" of ethiopia planned in 1288 to make a pilgrimage to jerusalem, following the practice of a number of his subjects; he was dissuaded from this project, but sent his "bishop" in his place. on his return leg, this bishop was detained by the "sultan of aden", who attempted to convert the ecclesiastic to islam; failing to do so, the sultan then had the bishop circumcised before releasing him. the "prince" then marched upon aden, and despite support from two other muslim allies, the sultan was defeated and his capital captured. a number of historians, including trimingham and pankhurst, identify the ruler with yagbe'u seyon, correct polo's reference to adal not the arabian seaport, and name zeila as the sultan's capital.