His first object was the reduction of Halicarnassus, where the enemy had now collected almost all the strength which he had remaining in this quarter. Memnon, who after the battle of the Granicus sent his wife and children as pledges of his fidelity to Darius, and had been invested by him with supreme authority in the west of Asia, and with the command of all his naval forces, had been long making preparations for the defence of the place, where he himself, with the Persian Orontobates, satrap of Caria, a numerous garrison of Greeks and barbarians, awaited the invader’s approach. They were animated by the presence of two Athenians, Ephialtes and Thrasybulus, who had come to offer their services against the common enemy. The fleet too, lying at the mouth of the harbour, was capable of rendering good service during a siege. The city, built on heights which rise abruptly in the form of a theatre from the sea, was naturally strong, and had been elaborately fortified, both with walls and a ditch forty-five feet in width, and about half as many in depth. Alexander, on his march from Miletus, made himself master of all the towns that lay between that city and Halicarnassus; and on his entrance into Caria, he was met by Ada, the widow of Idrieus, who surrendered her fortress of Alinda to him, begged leave to adopt him as her son, and placed herself under his protection. He then advanced towards Halicarnassus, and encamped at about half a mile from the walls.
He began by filling up the ditch, so as to enable his engines and wooden towers to approach the walls. The besieged made many vigorous sallies for the purpose of setting fire to the machines, but were always repulsed, and sometimes with great loss. Once a mad attempt of two Macedonian soldiers, who, having challenged one another over their cups to a trial of valour, undertook to storm the citadel on the land side alone, brought on an engagement, which was near becoming general, and might have ended in the capture of the city. For two towers and the intervening wall had been battered down by the engines; but before advantage was taken of the breach, the besieged built another brick wall in the form of a crescent behind it. Twice they made a desperate attempt to destroy the engines which Alexander brought to play on this new wall—the second time, at the instigation of Ephialtes, with their whole force; but they were defeated with great slaughter, in which Ephialtes himself fell, and it was believed that Alexander might then have stormed the place, but was induced to spare it by the hope that it would soon surrender. In fact, Memnon and Orontobates now despaired of defending it much longer, and resolved to abandon it. In the dead of the night they set fire to a wooden tower, and to some of the houses and magazines near the wall, and while the conflagration spread, made their escape, and crossed over to Cos, where it seems they had previously deposited their treasures. The garrison took refuge, some in the citadels, some in Arconnesus. Alexander immediately entered the city, and checked the progress of the flames. But as soon as he had become master of it, he razed it to the ground. He did not however think it worth while to stay, until he had dislodged the enemy from their remaining strongholds; but having committed the province to Ada, he left her, with about three thousand foot and two hundred horse, under a Macedonian officer, to reduce them. He himself pursued his march along the south coast of Asia Minor, to make himself master of the ports which might harbour the Persian fleet.
But as winter was now approaching, he determined, before he left Caria, to send a part of his troops, who had lately married when he set out on his expedition, back to Macedonia, to pass the winter at home. He gave the command of them to three of his generals, who were themselves in the same case; directing them on their return to bring with them as many fresh troops as they could raise. The measure was politic, as well as gracious; for his army had been much weakened to supply so many garrisons as were required for the conquered cities; and nothing was more likely to promote the levies in Macedonia, than the presence of the victorious warriors, whose return attested at once his success and his liberality. Another officer was sent to collect all the troops he could in Peloponnesus. Parmenion was ordered to proceed with the greater part of the cavalry and the baggage to Sardis, and thence into Phrygia, where he himself, after he should have traversed the coast of Lycia and Pamphylia, designed to meet him in the spring.