At the age of 20, Alexander's father was murdered. Alexander was determined to get the throne. He gained the support of Macedonian army. He wanted to take over Persia, India, and Greece during his time as king. Before going to war with Persia he conquered the Thracian Triballians, securing Macedonia's boarders.
At the end of his northern campaign, Alexander got word that Thebes, a Greek city-state, had revolted. Alexander marched his men in and wiped the Thebians out. He did this to prove that he was in charge and this caused many Greek alliances.
Next, Alexander wanted to conquer Egypt. Egypt fell without resistance and there he created one of the many cities called Alexandria. After that he went to Iran, India and Persia.