He then turned his attention to Greece where Thebes .
and Athens was threatening to lock the league with weapons purchased with Persian gold.
Also, Athens and Thebes were to unite in war against Macedon. In 335 B.C. Alexander decided to punish the city for what he regarded as treachery. The city was destroyed and its people sold into slavery or killed. All of the city's buildings were destroyed except for temples and the house of Pindar the poet. Pindar was long dead, but Alexander wanted to prove that even a Macedonian conqueror could be a Hellene. .
Alexander now took on a project that Philip had planned but never carried out: an invasion of Persia. His decision to do this was purely a political one. For a century Persia had interfered progressively more in Greek affairs and had constantly oppressed the Greek cities in Asia Minor. Alexander had personal reasons too. Enthusiastic for glory and for identification with Greece, Alexander knew no better way to win both than by attacking Greece's ancient enemy. In some ways the invasion, the longest military campaign ever undertaken, was a reckless task. It required a large army to move an enormous distance from its supply bases, through an unfamiliar country, against a power, infinitely rich in money and men. Furthermore, Persia was governed by a patriotic and devoted military caste that was gear to show its strength in war. However the enemy had a weakness. .
In 334 B.C. Alexander crossed the Hellespont. Something that his father had planned but not fully achieved. He defeated the Persian forces that were gathered on the Asian side of the River Granicus . After this victory Alexander sent three hundred suits of Persian armor back to Athens. Alexander could be compared to Napoleon in swiftness and in movement, but Alexander could be patient as well. As he showed in his siege of the fortress of Tyre, which lasted for about seven months. The old harbor of Tyre had been abandoned for some time, and the Tyrians were now firmly enclosed behind massive walls on an island that was half a mile from the coast.
