Like the Roman permanent camps, these fortified cities had a castle or citadel, which was almost invariably placed on the highest point of the site, and adjoined the enceinte so as to command and defend the town, and, at the same time, be in a position to receive supplies and reinforcements from without. Within the castle, again, was a still further security in the donjon, or redoubt, which was detached from the other works, and often had a ditch and an enclosing wall, or _chemise_, of its own, and could be held after all the other defences had succumbed. Such walls as those of the Visigoths at Carcassonne were sufficient to resist the means of attack employed from the fifth to the eleventh century. At that period of revival a great improvement took place all round, and there can be no doubt that the early Crusaders learned much in the East with regard to the science of attack and defence of strongholds. In the eleventh and twelfth centuries, towers like those of the Normans were erected, which depended for their security on the natural strength of the site, and the great height and thickness of the walls--their height protecting them against assault by scaling, and their mass and position against the mine and battering ram. They were further strengthened with outer walls and ditches. [Illustration: FIG. 111. CARCASSONNE--OUTER AND INNER WALLS, N. SIDE.] A very interesting description, illustrative of the manner of carrying on and resisting siege operations, is quoted by Viollet-le-Duc from a report rendered by Guillaume des Ormes, Seneschal of Carcassonne, to Queen Blanche, on the raising of the siege of that town by Trenceval in 1240. The report details how the besiegers and defenders battered one another with mongonneaux; how they mined and countermined; how part of the wall was sapped, and a breach formed, inside of which the defenders raised a wooden _bretêche_, crowned with hoards, and armed with archers. On St Louis’ return from his first crusade, he was desirous to strengthen his position in the newly-acquired dominions of the Count of Toulouse. He, therefore, resolved to make a strong citadel of Carcassonne. For this purpose the houses in the suburbs were cleared away, and a new town, or bastide, was established, as above mentioned, for the ejected inhabitants on the opposite side of the river, where the new town now stands.