He had now collected many engineers both from Cyprus and the whole of Phoenicia, and many engines of war had been constructed,[323] some upon the mole, others upon vessels used for transporting horses, which he brought with him from Sidon, and others upon the triremes which were not fast sailers. When all the preparations had been completed they brought up the engines of war along the mole that had been made and also began to shoot from ships moored near various parts of the wall and making trial of its strength. The Tyrians erected wooden towers on their battlements opposite the mole, from which they might annoy the enemy; and if the engines of war were brought near any other part, they defended themselves with missiles and shot at the very ships with fire-bearing arrows, so that they deterred the Macedonians from approaching the wall. Their walls opposite the mole were about one hundred and fifty feet high, with a breadth in proportion, and constructed with large stones imbedded in gypsum. It was not easy for the horse-transports and the triremes of the Macedonians, which were conveying the engines of war up to the wall, to approach the city, because a great quantity of stones hurled forward into the sea prevented their near assault. These stones Alexander determined to drag out of the sea; but this was a work accomplished with great difficulty, since it was performed from ships and not from the firm earth; especially as the Tyrians, covering their ships with mail, brought them alongside the anchors of the triremes, and cutting the cables of the anchors underneath, made anchoring impossible for the enemy’s ships. But Alexander covered many thirty-oared vessels with mail in the same way, and placed them athwart in front of the anchors, so that the assault of the ships was repelled by them. But, notwithstanding this, divers under the sea secretly cut their cables. The Macedonians then used chains to their anchors instead of cables, and let them down so that the divers could do no more harm. Then, fastening slip-knots to the stones, they dragged them out of the sea from the mole; and having raised them aloft with cranes, they discharged them into deep water, where they were no longer likely to do injury by being hurled forward. The ships now easily approached the part of the wall where it had been made clear of the stones which had been hurled forward. The Tyrians being now reduced to great straits on all sides, resolved to make an attack on the Cyprian ships, which were moored opposite the harbour turned towards Sidon. For a long time they spread sails across the mouth of the harbour, in order that the filling of the triremes might not be discernible; and about the middle of the day, when the sailors were scattered in quest of necessaries, and when Alexander usually retired from the fleet to his tent on the other side of the city, they filled three quinqueremes, an equal number of quadriremes and seven