371 BC
Battle of Leuctra
The setting
Leuctra, Boeotia, Greece (SW of Thebes)
Open plain suitable for hoplite phalanx and cavalry; the two armies deployed facing each other on level ground.
Reveal the outcome
Recorded sideThebes / Boeotian League (Epaminondas)
Recorded resultvictory
Decisive Theban victory; King Cleombrotus killed
How the atlas explains it
Epaminondas massed his best troops in a column up to 50 ranks deep on his left, opposite the Spartan king and elite right, while refusing (echeloning back) his weaker center and right so they would not engage prematurely. The Theban cavalry cleared the field, then the deep left, spearheaded by the Sacred Band, smashed the Spartan right before the rest of the line was committed; Cleombrotus fell and the loss of so many Spartiates broke Spartan cohesion.
What followed
Ended the myth of Spartan invincibility on land and broke Spartan hegemony in Greece; the disproportionate loss of Spartiate manpower crippled Sparta permanently. The oblique/concentrated-wing tactic influenced Philip and Alexander.