On Alexander’s part there was no haste in turning to the interior. Instead of following Darius, he remained on the sea coast, while Parmenio was sent to Damascus with half the Greek army, to seize the treasure left there by Darius before the battle of Issus. Alexander with the rest of the army turned south to the conquest of the great island city of Phœnicia, which unlike its smaller neighbors had refused to surrender and had declared its neutrality to Alexander. Tyre was the center of Persian sea power, and so long as it remained independent its fleet could be used against the Greek king, either on the sea itself or as an instrument for creating disturbances in continental Greece. The siege of Tyre involved special difficulties; not only were its walls high and strong, but it was situated on an island separated from the mainland by a shallow body of water. As Alexander had no fleet adequate to conduct aggressive operations from the open sea against the city, he planned to bring up his siege engines against the walls from the land side, by building a causeway over the shallow body of water. The defenders of the town tried repeatedly and with great bravery to prevent such an approach from being made. Tyre’s own commercial competitors, Cyprus and the less important Phœnician cities, including Sidon, placed their navies at Alexander’s disposition, and with their ships he began to operate from the sea. The situation of the town was desperate, but its people made a defense as desperate and as resourceful as their daughter city Carthage in later days against the Romans. When the causeway was finally constructed, the walls on this side, being 150 feet high and enormously thick, were not damaged by the siege engines. Accordingly Alexander changed his plans quickly; the engines were mounted in vessels and a breach was effected in one of the battlements extending along the harbor. While the Macedonians were now able to penetrate the city, they met with heavy resistance from the besieged townsmen, and the occupation of Tyre was only effected by the protection of Alexander’s naval allies, who forced an entrance into the two harbors, and so drew off a portion of the defenders from the side where the Greeks were making their attack. The stubborn defense cost the Tyrians 8000 men, and of the prisoners 3000 were sold as slaves. On the Macedonian side the loss was small, only amounting to 400 men, but no mention is made of the losses of the allied fleets. The siege of Tyre lasted seven months, the city falling in July, 332. The long delay was worth while, for the successful issue showed how invincible was the generalship of the Greek leader. By the possession of the city he held the key to the control of the eastern Mediterranean.