Epaminondas

Epaminondas was the major force in Thebes gaining its independence from Sparta after his impressive victory over the Spartans in the Battle of Leuctra in 371 B.C. As Thebes rose to prominence he won a victory over Sparta and Athens in the Battle of Mantinea in 362 B.C., but was killed in that battle. The prominent position of Thebes would quickly subside to Philip of Macedon. What he accomplished was remarkable, but little known since it didn't last long after his death.

Sources

Encyclopedia of Military History, Dupuy & Dupuy, 1979