In this lecture, Professor Kagan describes the growth of a new power: Thebes. Under the leadership of Epaminondas and Pelopidas, Thebes grows into a major power among the Greek cities. In fact, the Thebans even rout the Spartans in a standard hoplite battle in the battle of Leuctra. Finally, Professor Kagan points out that by the time of Theban hegemony, the Greek world had experienced so many wars and conflicts that it opened the door to a powerful leader: Philip of Macedon.