Thebes defeated Sparta at the Battle of Leuctra in 371 BCE.
The Theban army was commanded by Epaminondas and Pelopidas. Epaminondas used an unusually deep concentration of troops on his left wing, refusing to engage the strongest Spartan forces immediately and breaking the traditional hoplite pattern.
Spartan king Cleombrotus I was killed during the battle. The defeat ended Sparta’s long dominance over much of Greece and allowed Thebes to become the leading military power for a time.
Leuctra is often remembered as a turning point in Greek warfare. The following year, Epaminondas invaded the Peloponnese and helped restore the independence of Messenia, a major blow to Spartan power.