Battle of Leuctra
The Battle of Leuctra was part of an attempt by Thebes to win its indepdence from Spartan control. The war went from 379 to 371 B.C. and the battle was fought in 371 B.C. King Cleombrotus of Sparta had 11,000 men to 6,000 for the Epaminondas, the Theban leader. In a shocking turn of events, the usually unbeatable Spartans were defeated after Epaminondas quadrupled the depth of his left wing. Holding in the center and the right side, he overwhelmed the Spartans with his left wing and turned their flank. The Spartans lost over 2,000 men. Spartan military prestige was shattered never to recover and Thebes gained its independence and temporary supremacy in Greece.
Encyclopedia of Military History, Dupuy & Dupuy, 1979