Of all the foes Alexander wanted to best, his primary objective was Darius III. Head of the Persian Empire, Darius was used to winning his battles. But he was not accustomed to opposing adversaries whose military genius and strategy were equal to, or better than, his own.
While Alexander used the strategies and battle formations developed by his father, his ability to improvise on short notice was just one mark of his outstanding leadership.
One of his early plans was to liberate the Greek cities along the eastern Aegean Sea, on the mainland of Asia Minor. Crossing the sea with his men, Alexander's first stop was at Troy where he visited the grave of Achilles and paid homage to the gods. (That moment was artistically depicted, nearly 2000 years later, by the German painter Johann Schoenfeld.) He then turned south with his men, personally leading the Companion Cavalry.
Darius, meanwhile, was at his remote capital in Susa. Alexander's reputation was still in-the-making, and the Persian leader thought his troops could be capably managed by the governors of his western provinces. ( They were aided by a Greek mercenary, Memnon the Rhodian, who had already proved his mettle in prior Macedonian battles).
In 333, Alexander met Darius at the mountain pass at Issus. Although greatly outnumbered, the Macedonian leader took advantage of the narrow field of battle and worked it to his advantage. Not used to such brilliant strategy from his opponents, Darius was shocked by Alexander's ability. A famous mosaic, discovered in the excavations of Pompeii, graphically depicts Darius' surprise.
Believed to be based on a contemporary drawing, the Pompeii mosaic is the source of the most commonly used pictures of both Alexander and Darius. The work is now called the "Alexander Mosaic" and was originally found at the House of the Faun in Pompeii. It is maintained today at the Museo Archeologico Nazionale Napoli (the National Archeology Museum in Naples). It is believed the entire work portrays the battle of Issus.
Despite his surprise at Alexander's tactics, Darius escaped.
Thereafter, marching down the Mediterranean Coast, into Damascus, Alexander captured the family and war chest of the Persian ruler. As he victoriously continued down the Phoenician coast, he easily captured every city except Tyre. It took a seven-month siege before that city gave up as well.
Having secured the eastern Aegean, Alexander and his men headed to Egypt where he founded the city of Alexandria. Ultimately one of the cultural centers of the known world, it was home of the famous lighthouse (one of the wonders of the ancient world) and of the Great Library (a center of learning until it was destroyed).
Chasing Darius was still on Alexander's mind as he left Egypt in 331. Having captured territory between the Tigris and Euphrates Rivers (today's Iraq), Alexander's men found the Persians at the Plain of Gaugamela.
This battle, and its aftermath, would mark a turning point for the Persian leader.