In 340B.C., when Philip went to fight rebels in Byzantium, Alexander, only sixteen years old, was left as regent to control in Philip's absence. Alexander's being left in power indicates that he had proven himself in battle. During his reign as regent, the Maedi of northern Macedonia revolted. Alexander put down the revolt, drove the survivors north, and established a Greek colony that he named Alexandroupolis. .
Unfortunately, Alexander did not get along well with his father. Alexander was much closer to his mother, Olympias. The fact that she was a foreigner from Epirus (present day Albania) only served to drive a wedge between her and Philip. This foreign heritage was also used against Alexander when Philip married a Macedonian named Cleopatra. Some stated that Alexander was not a legitimate heir due to his foreign bloodline and that if Philip fathered a child by Cleopatra, it would be a more fitting ruler of Macedonia than Alexander. At the wedding ceremony for Cleopatra and Philip, the bride's father commented on Alexander's being an unfit heir. Enraged, Alexander threw his cup at the man (some speculate he may even have killed him). Philip then charged at his son in defense of his father-in-law, but the king was drunk and fell on his face. Soon afterward, Alexander moved his mother back to her homeland of Epirus, and he went to Illyria. Alexander later returned, but he and his father remained family in name only. It is even speculated that Olympias may have been involved in the murder or Philip.
After his father's murder in 336B.C., Alexander assumed the throne of Macedonia. Immediately, there were rebellions from cities like Athens and Thebes and from barbarians, all of whom pledged their allegiance to Philip and not to a mere child. Alexander's advisors suggested he let the Greek cities go and be gentle with the barbarians, but Alexander felt that it was best to be decisive and swift.
