Ancient Greek warriors became the premiere warriors of their classical world. Through intense internal warfare they perfected heavy infantry tactics and when they were united they were able to defeat an invasion by Persia, the super power of their day. The heavily outnumbered Greek warriors called hoplites used superior tactics, training and arms to defeat two massive invasions. However, the Greeks returned to their incessant warfare once their common enemy was defeated. Philip of Hellenized Macedonia, king of what the Greeks considered a barbarian kingdom to their North, learned and even improved the Greeks phalanx formation and eventually dominated Greece. His son, Alexander the Great, then took the Macedonian and Greek warriors he inherited from his father and conquered the known world. Greek culture, called Hellenistic, became dominate from Sicily to India.