The emir of Menteshe invaded Rhodes about 1300.[69] But he did not succeed in entirely conquering it. For ten years Greek and Turk struggled for the mastery of this gateway to the Aegaean Sea. Then suddenly an outside foe arrived and made the double conquest of Christian and Moslem alike. The Knights of St. John of Jerusalem, driven from the Holy Land by the Egyptian conquest, had tired of their refuge in Cyprus.[70] After vainly endeavouring to negotiate with Constantinople for the transfer of the proprietary rights of the island to their order, they attacked and conquered Rhodes with the encouragement of Philippe le Bel and the Pope. This great event, equally disastrous to Turk and Greek, happened on August 15, 1310. For more than two centuries they were able to maintain at Rhodes a citadel and outpost of Christianity in a part of the world which was rapidly becoming _in partibus infidelium_.[71] The emir of Menteshe made a strenuous effort to recapture Rhodes. The Hospitallers, attacked before they had time to repair and strengthen the fortifications of the island, were saved only by the timely arrival and heroism of Amadeus of Savoy. This is said to be the origin of the arms of Savoy, which are perpetuated on the flag of modern Italy, and of the motto of the sovereigns of Piedmont--F E R T, _Fortitudo Eius Rhodum Tenuit_.[72] The historians of Rhodes, as well as the chroniclers of the House of Savoy, declare that Osman was the leader of the Turks who attacked Rhodes in 1310 or 1311,[73] and that he was instigated by the Genoese.[74] VIII But while Osman was, in the minds of these and other later historians, supposed to be attacking Rhodes and making himself master of Asia Minor, he stayed within the narrow limits of his little principality, from which he never issued forth, as far as we know, during his circumscribed career. For he had, within a day’s journey of his residence, the imperial cities of Brusa and Nicaea, whose walls were far too strong for the infant Osmanlis. A little more to the north-west, in a position of unrivalled strategic importance, defending the logical[75] waterway to Constantinople from the valley of the Sangarius, lay Nicomedia.