The Theban League was a confederation of city-states in ancient Greece, centered around the city of Thebes. Established in the 4th century BCE, it aimed to counter the dominance of Sparta and later Athens. The league was notable for its military strength, particularly during the Battle of Leuctra in 371 BCE, where it achieved a significant victory over the Spartans. The league's influence peaked under the leadership of Epaminondas, who reformed its military tactics and strategies. However, its power waned after his death, leading to internal conflicts and the eventual dissolution of the league by the rise of Macedonia under Philip II.