A march of sixteen days brought Alexander to Sestos, where a large fleet and a number of transports had been collected for the embarkation of his army. He steered with his own hand the vessel in which he sailed towards the very spot where the Achaeans were said to have landed when proceeding to the Trojan war. He was, as we have said, a great admirer of Homer, a copy of whose works he always carried with him; and on landing on the Asiatic coast he made it his first business to visit the plain of Troy. He then proceeded to Sigeum, where he crowned with a garland the pillar said to mark the tumulus of his mythical ancestor Achilles, and, according to custom, ran round it naked with his friends.

Alexander then marched northwards along the coast of the Propontis. The satraps of Lydia and Ionia, together with other Persian generals, were encamped on the river Granicus, with a force of 20,000 Greek mercenaries, and about an equal number of native cavalry, with which they prepared to dispute the passage of the river. A Rhodian, named Memnon, had the chief command. The veteran general Parmenio advised Alexander to delay the attack till the following morning; to which he replied, that it would be a bad omen at the beginning of his expedition, if, after passing the Hellespont, he should be stopped by a paltry stream. Thereupon he directed his cavalry to cross the river, and followed himself at the head of the phalanx. The passage, however, was by no means easy. The stream was in many parts so deep as to be hardly fordable, and the opposite bank was steep and rugged. The cavalry had great difficulty in maintaining their ground till Alexander came up to their relief. He immediately charged into the thickest of the fray, and exposed himself so much that his life was often in imminent danger, and on one occasion was saved only by the interposition of his friend Clitus. Having routed the Persians, he next attacked the Greek mercenaries, 2000 of whom were made prisoners, and the rest nearly all cut to pieces, In this engagement he killed two Persian officers with his own hand.

Alexander now marched southwards towards Sardis, which surrendered before he came within sight of its walls. Having left a garrison in that city, he arrived after a four days' march before Ephesus, which likewise capitulated on his approach. Magnesia, Tralles, and Miletus next fell into his hands, the last after a short siege. Halicarnassus made more resistance. It was obliged to be regularly approached; but at length Memnon, finding it no longer tenable, set fire to it in the night, and crossed over to Cos. Alexander caused it to be razed to the ground, and pursued his march along the southern coast of Asia Minor, with the view of seizing those towns which might afford shelter to a Persian fleet. The winter was now approaching, and Alexander sent a considerable part of his army under Parmenio into winter-quarters at Sardis. He also sent back to Macedonia such officers and soldiers as had been recently married, on condition that they should return in the spring with what reinforcements they could raise; and with the same view he despatched an officer to recruit in the Peloponnesus. Meanwhile he himself with a chosen body proceeded along the coasts of Lycia and Pamphylia, having instructed Parmenio to rejoin him in Phrygia in the spring, with the main body. After he had crossed the Xanthus most of the Lycian towns tendered their submission. On the borders of Lycia and Pamphylia, Mount Climax, a branch of the Taurus range, runs abruptly into the sea, leaving only a narrow passage at its foot, which is frequently overflowed. This was the case at the time of Alexander's approach. He therefore sent his main body by a long and difficult road across the mountains to Perge; but he himself who loved danger for its own sake, proceeded with a chosen band along the shore, wading through water that was breast-high for nearly a whole day. Then forcing his way northwards through the barbarous tribes which inhabited the mountains of Pisidia, he encamped in the neighbourhood of Gordium in Phrygia. Here he was rejoined by Parmenio and by the new levies from Greece. Gordium had been the capital of the early Phrygian kings, and in it was preserved with superstitious veneration the chariot or waggon in which the celebrated Midas, the son of Gordius, together with his parents, had entered the town, and in conformity with an oracle had been elevated to the monarchy. An ancient prophecy promised the sovereignty of Asia to him who should untie the knot of bark which fastened the yoke of the waggon to the pole. Alexander repaired to the Acropolis, where the waggon was preserved, to attempt this adventure. Whether he undid the knot by drawing out a peg, or cut it through with his sword, is a matter of doubt; but that he had fulfilled the prediction was placed beyond dispute that very night by a great storm of thunder and lightning.

In the spring of 333 Alexander pursued his march eastwards, and on arriving at Ancyra received the submission of the Paphlagonians. He then advanced through Cappadocia without resistance; and forcing his way through the passes of Mount Taurus (the PYLAE CILICIAE), he descended into the plains of Cilicia. Hence he pushed on rapidly to Tarsus, which he found abandoned by the enemy. Whilst still heated with the march Alexander plunged into the clear but cold stream of the Cydnus, which runs by the town. The result was a fever, which soon became so violent as to threaten his life. An Acarnanian physician, named Philip, who accompanied him, prescribed a remedy; but at the same time Alexander received a letter informing him that Philip had been bribed by Darius, the Persian king, to poison him. He had however, too much confidence in the trusty Philip to believe the accusation and handed him the letter whilst he drank the draught. Either the medicine, or Alexander's youthful constitution, at length triumphed over the disorder. After remaining some time at Tarsus, he continued his march along the coast to Mallus, where he first received certain tidings of the great Persian army, commanded by Darius in person. It is said to have consisted of 600,000 fighting men, besides all that train of attendants which usually accompanied the march of a Persian monarch. Alexander found Darius encamped near Issus on the right bank of the little river Pinarus. The Persian king could hardly have been caught in a more unfavourable position, since the narrow and rugged plain between Mount Amanus and the sea afforded no scope for the evolutions of large bodies, and thus entirely deprived him of the advantage of his numerical superiority. Alexander occupied the pass between Syria and Cilicia at midnight, and at daybreak began to descend into the plain of the Pinarus, ordering his troops to deploy into line as the ground expanded and thus to arrive in battle-array before the Persians. Darius had thrown 30,000 cavalry and 20,000 infantry across the river, to check the advance of the Macedonians; whilst on the right bank were drawn up his choicest Persian troops to the number of 60,000, together with 30,000 Greek mercenaries, who formed the centre, and on whom he chiefly relied. These, it appears, were all that the breadth of the plain allowed to be drawn up in line. The remainder of the vast host were posted in separate bodies in the farther parts of the plain, and were unable to take any share in the combat. Darius placed himself in the centre of the line in a magnificent state chariot. The banks of the Pinarus were in many parts steep, and where they were level Darius had caused them to be intrenched. As Alexander advanced, the Persian cavalry which had been thrown across the river were recalled; but the 20,000 infantry had been driven into the mountains, where Alexander held them in check with a small body of horse. The left wing of the Macedonians, under the command of Parmenio, was ordered to keep near the sea, to prevent being outflanked. The right wing was led by Alexander in person, who rushed impetuously into the water, and was soon engaged in close combat with the Persians. The latter were immediately routed; but what chiefly decided the fortune of the day was the timidity of Darius himself, who, on beholding the defeat of his left wing, immediately took to flight. His example was followed by his whole army. One hundred thousand Persians are said to have been left upon the field. On reaching the hills Darius threw aside his royal robes his bow and shield, and, mounting a fleet courser, was soon out of reach of pursuit. The Persian camp became the spoil of the Macedonians; but the tent of Darius, together with his chariot, robes, and arms, was reserved for Alexander himself. It was now that the Macedonian king first had ocular proof of the nature of Eastern royalty. One compartment of the tent of Darius had been fitted up as a bath, which steamed with the richest odours; whilst another presented a magnificent pavilion, containing a table richly spread for the banquet of Darius. But from an adjoining tent issued the wail of female voices, where Sisygambis the mother, and Statira the wife of Darius, were lamenting the supposed death of the Persian monarch. Alexander sent to assure them of his safety, and ordered them to be treated with the most delicate and respectful attention.

Such was the memorable battle of Issus, fought in November, B.C. 333. A large treasure which Parmenio was sent forward with a detachment to seize, fell into the hands of the Macedonians at Damascus. Another favourable result of the victory was that it suppressed some attempts at revolt from the Macedonian power, which with the support of Persia, had been manifested in Greece. But, in order to put a complete stop to all such intrigues, which chiefly depended on the assistance of a Persian fleet, Alexander resolved to seize Phoenicia and Egypt, and thus to strike at the root of the Persian maritime power.

Meanwhile, Darius, attended by a body of only 4000 fugitives, had crossed the Euphrates at Thapsacus. Before he had set out from Babylon the whole forces of the empire had been summoned; but he had not thought it worth while to wait for what he deemed a merely useless encumbrance; and the more distant levies, which comprised some of the best troops of the empire, were still hastening towards Babylon. In a short time, therefore, he would be at the head of a still more numerous host than that which had fought at Issus; yet he thought it safer to open negotiations with Alexander than to trust to the chance of arms. With this view he sent a letter to Alexander, who was now at Marathus in Phoenicia, proposing to become his friend and ally; but Alexander rejected all his overtures, and told him that he must in future be addressed not in the language of an equal, but of a subject.

As Alexander advanced southwards, all the towns of Phoenicia hastened to open their gates; the inhabitants of Sidon even hailed him as their deliverer. Tyre, also, sent to tender her submission; but coupled with reservations by no means acceptable to a youthful conqueror in the full tide of success. Alexander affected to receive their offer as an unconditional surrender, and told them that he would visit their city and offer sacrifices to Melcart, a Tyrian deity, who was considered as identical with the Grecian Hercules. This brought the matter to an issue. The Tyrians now informed him that they could not admit any foreigners within their walls, and that, if he wished to sacrifice to Melcart, he would find another and more ancient shrine in Old Tyre, on the mainland. Alexander indignantly dismissed the Tyrian ambassadors, and announced his intention of laying siege to their city. The Tyrians probably deemed it impregnable. It was by nature a place of great strength, and had been rendered still stronger by art. The island on which it stood was half a mile distant from the mainland; and though the channel was shallow near the coast, it deepened to three fathoms near the island. The shores of the island were rocky and precipitous, and the walls rose from the cliffs to the height of 150 feet in solid masonry. As Alexander possessed no ships, the only method by which he could approach the town was by constructing a causeway, the materials for which were collected from the forests of Libanus and the ruins of Old Tyre. After overcoming many difficulties the mole was at length pushed to the foot of the walls; and as soon as Alexander had effected a practicable breach, he ordered a general assault both by land and sea. The breach was stormed under the immediate inspection of Alexander himself; and though the Tyrians made a desperate resistance, they were at length overpowered, when the city became one wide scene of indiscriminate carnage and plunder. The siege had lasted seven months, and the Macedonians were so exasperated by the difficulties and dangers they had undergone that they granted no quarter. Eight thousand of the citizens are said to have been massacred; and the remainder, with the exception of the king and some of the principal men, who had taken refuge in the temple of Melcart, were sold into slavery to the number of 30,000. Tyre was taken in the month of July in 332.

Whilst Alexander was engaged in the siege of Tyre, Darius made him further and more advantageous proposals. He now offered 10,000 talents as the ransom of his family, together with all the Provinces west of the Euphrates, and his daughter Barsine in marriage, as the conditions of a peace. When these offers were submitted to the council Parmenio was not unnaturally struck with their magnificence, and observed, that were he Alexander he would accept them. "And so would I," replied the king, "were I Parmenio." Darius, therefore, prepared himself for a desperate resistance.

After the fall of Tyre, Alexander marched with his army towards Egypt, whilst his fleet proceeded along the coast. Gaza, a strong fortress on the sea-shore, obstinately held out, and delayed his progress three or four months. After the capture of this city Alexander met his fleet at Pelusium, and ordered it to sail up the Nile as far as Memphis, whither he himself marched with his army across the desert. He conciliated the affection of the Egyptians by the respect with which he treated their national superstitions, whilst the Persians by an opposite line of conduct had incurred their deadliest hatred. He then sailed down the western branch of the Nile, and at its mouth traced the plan of the new city of Alexandria, which for many centuries continued to be not only the grand emporium of Europe, Africa, and India, but also the principal centre of intellectual life. Being now on the confines of Libya, Alexander resolved to visit the celebrated oracle of Zeus (Jupiter) Ammon, which lay in the bosom of the Libyan wilderness. The conqueror was received by the priests with all the honours of sacred pomp. He consulted the oracle in secret, and is said never to have disclosed the answer which he received; though that it was an answer that contented him appeared from the magnificence of the offerings which he made to the god. Some say that Ammon saluted him as the son of Zeus.

Alexander returned to Phoenicia in the spring of 331. He then directed his march through Samaria, and arrived at Thapsacus on the Euphrates about the end of August. After crossing the river he struck to the north-east through a fertile and well-supplied country. On his march he was told that Darius was posted with an immense force on the left bank of the Tigris; but on arriving at that river he found nobody to dispute his passage. He then proceeded southwards along its banks, and after four days' march fell in with a few squadrons of the enemy's cavalry. From some of these who were made prisoners Alexander learned that Darius was encamped with his host on one of the extensive plains between the Tigris and the mountains of Kurdistan, near a village called Gaugamela (the Camel's House). The town of Arbela, after which the battle that ensued is commonly named, lay at about twenty miles distance, and there Darius had deposited his baggage and treasure. That monarch had been easily persuaded that his former defeat was owing solely to the nature of the ground; and, therefore, he now selected a wide plain for an engagement, where there was abundant room for his multitudinous infantry, and for the evolutions of his horsemen and charioteers. Alexander, after giving his army a few days' rest, set out to meet the enemy soon after midnight, in order that he might come up with them about daybreak. On ascending some sand-hills the whole array of the Persians suddenly burst upon the view of the Macedonians, at the distance of three or four miles. Darius, as usual, occupied the centre, surrounded by his body-guard and chosen troops. In front of the royal position were ranged the war-chariots and elephants, and on either side the Greek mercenaries, to the number, it is said, of 50,000. Alexander spent the first day in surveying the ground and preparing for the attack; he also addressed his troops, pointing out to them that the prize of victory would not be a mere province, but the dominion of all Asia. Yet so great was the tranquillity with which he contemplated the result, that at daybreak on the following morning, when the officers came to receive his final instructions, they found him in a deep slumber. His army, which consisted only of 40,000 foot and 7000 horse, was drawn up in the order which he usually observed, namely, with the phalanx in the centre in six divisions, and the Macedonian cavalry on the right, where Alexander himself took his station. The Persians, fearful of being surprised, had stood under arms the whole night, so that the morning found them exhausted and dispirited. Some of them, however, fought with considerable bravery; but when Alexander had succeeded in breaking their line by an impetuous charge, Darius mounted a fleet horse and took to flight, as at Issus, though the fortune of the day was yet far from having been decided. At length, however, the rout became general. Whilst daylight lasted Alexander pursued the flying enemy as far as the banks of the Lycus, or Greater Zab, where thousands of the Persians perished in the attempt to pass the river. After resting his men a few hours Alexander continued the pursuit at midnight in the hope of overtaking Darius at Arbela. The Persian monarch, however, had continued his flight without stopping; but the whole of the royal baggage and treasure was captured.