On his return, he crushed in a single week the threatening Illyrians and then hastened to Thebes, which had revolted. He took the city by storm and razed it, sparing only the temples of the Gods and the house of the Greek lyric poet Pindar, and selling the surviving inhabitants, about 8000 in number, into slavery. Alexander’s promptness in crushing the revolt of Thebes brought the other Greek states into instant and abject submission. Alexander began his war against Persia in the spring of 334 BC by crossing the Hellespont (modern Dardanelles) with an army of 35,000 Macedonian and Greek troops. His chief officers, all Macedonians, included Antigonus, Ptolemy, and Seleucus.
At the river Granicus, near the ancient city of Troy, he attacked an army of Persians and Greek hoplites (mercenaries) totaling 40,000 men. His forces defeated the enemy and, according to tradition, lost only 110 men; after this battle all the states of Asia Minor submitted to him. In passing through Phrygia, he is said to have cut with his sword the Gordian knot. Continuing to advance southward, Alexander encountered the main Persian army, commanded by King Darius III, at Issus, in North-eastern Syria. The size of Darius’s army is unknown; the ancient tradition that it contained 500,000 men is now considered a fantastic exaggeration. The Battle of Issus, in 333, ended with a great victory of Alexander.
Cut off from his base, Darius fled northward, abandoning his mother, wife, and children to Alexander, who treated them with the respect due to royalty. Tyre, a strongly fortified seaport, offered obstinate resistance, but Alexander took it by storm in 332 after a siege of seven months. Alexander captured Gaza next and then passed on into Egypt, where he was greeted as a deliverer. By these successes he secured control of the entire eastern Mediterranean coastline. Later in 332 he founded, at the mouth of the Nile River, the city of Alexandria.
Then he marched towards India. On the bank of Indus River, he faced a stiff resistance from a brave Indian king named Porus. Porus was defeated; however, seeing his brevity Alexander freed him with dignity. By this time the soldiers of Alexander were very tired, they refused to proceed towards Indian mainland. Alexander decided to return to his kingdom disgusted. He left Seleucus in India to preserve his conquered territory, and left for Macedonia. He was disheartened and became a heavy drunkard. He seriously suffered from malaria and died in 326 BC in Egypt.