Thus it was that when, in 1346, Edward III. had beaten Philippe VI. at the battle of Crecy, the first use he made of his victory was to march upon Calais, and lay siege to it. The walls were exceedingly strong and solid, mighty defenses of masonry, of huge thickness and like rocks for solidity, guarded it, and the king knew that it would be useless to attempt a direct assault. Indeed, during all the Middle Ages, the modes of protecting fortifications were far more efficient than the modes of attacking them. The walls could be made enormously massive, the towers raised to a great height, and the defenders so completely sheltered by battlements that they could not easily be injured and could take aim from the top of their turrets, or from their loophole windows. The gates had absolute little castles of their own, a moat flowed round the walls full of water, and only capable of being crossed by a drawbridge, behind which the portcullis, a grating armed beneath with spikes, was always ready to drop from the archway of the gate and close up the entrance. The only chance of taking a fortress by direct attack was to fill up the moat with earth and faggots, and then raise ladders against the walls; or else to drive engines against the defenses, battering-rams which struck them with heavy beams, mangonels which launched stones, sows whose arched wooden backs protected troops of workmen who tried to undermine the wall, and moving towers consisting of a succession of stages or shelves, filled with soldiers, and with a bridge with iron hooks, capable of being launched from the highest story to the top of the battlements. The besieged could generally disconcert the battering- ram by hanging beds or mattresses over the walls to receive the brunt of the blow, the sows could be crushed with heavy stones, the towers burnt by well-directed flaming missiles, the ladders overthrown, and in general the besiegers suffered a great deal more damage than they could inflict. Cannon had indeed just been brought into use at the battle of Crecy, but they only consisted of iron bars fastened together with hoops, and were as yet of little use, and thus there seemed to be little danger to a well-guarded city from any enemy outside the walls.