In 371BCE, Thebes dealt Sparta, the reigning hegemon of Greece, a blow it would never recover from. An innovative mix of hoplite tactics allowed Theban General Epaminondas to win a landmark strategic victory that put Thebes on the map... for about 30 years before they screwed it all up.
Sources:
Hanson, Victor Davis, "The Leuktra Mirage"
Ray Jr., Frank Eugene, "Greek and Macedonian Land Battles of the 4th Century BC," McFarland, 2012.
Xenophon, "Hellenica"
Battle (Normal)-Boxcat Games
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