_enceinte_, borrowed from the Byzantines, the inner line of which commanded the outer, and was sufficiently near to allow its defenders to engage, should assailants have carried the first barrier; secondly, stone machicolations in place of the wooden _hourds_ or timber scaffoldings which were retained in France till the close of the thirteenth century; and finally, the talus, a device by which the thickness of the walls was tripled at the base, thus affording increased security against the arts of the sapper and the earthquake shocks so frequent in the East. [Illustration: 166. FORTRESS OF KALAAT-EL-HOSN IN SYRIA (KRAK OF THE KNIGHTS). SECTION, AS RESTORED BY M. G. REY.] [Illustration: 166A. FORTRESS DE KALAAT-EL-HOSN IN SYRIA (KRAK OF THE KNIGHTS). AS RESTORED BY M. G. REY] The buildings of the second class belong to the school of the Knights Templars. Their characteristic features are the towers, invariably square or oblong in shape, and projecting but slightly from the curtains. The fortress of Kalaat-el-Hosn,[60] or _Krak_ of the knights, commanded the pass through which ran the roads from Homs and Hamah to Tripoli and Tortosa, and was a military station of the first importance. Together with the castles of Akkar, Arcos, La Colée, Chastel-Blanc, Areynieh, Yammour, Tortosa, and Markab, and the various auxiliary towers and posts, it constituted a system of defence designed to protect Tripoli from the incursions of the Mahometans, who retained their hold on the greater part of Syria.... The _Krak_, which was built under the direction of the Knights Hospitallers, has a double _enceinte_, separated by a wide ditch partly filled with water. The inner wall forms a reduct, and rising above the outer enclosure commands its defences. It also encompasses the various dependencies of the castle, the great hall, chapel, domestic buildings, and magazines. A long vaulted passage, easy of defence, was the only entrance to the place. To the north and west the outer line consisted of a curtain flanked by rounded turrets, and crowned by machicolations, which formed a continuous scaffolding of stone along the greater part of the _enceinte_. [60] _Étude sur les Monuments de l'Architecture Militaire des croisés en Syrie_, by G. Rey; Paris, 1871. [Illustration: 167. CITY OF CARCASSONNE. PLAN (THIRTEENTH CENTURY)] The action of the East upon the West was manifested in the thirteenth and fourteenth centuries by the application to the fortification of Carcassonne and Aigues-Mortes of methods in use among the Crusaders in Syria. This oriental influence is apparent at Carcassonne in the double _enceinte_ borrowed from Syrian fortresses.