The Battle of Leukter took place in 371 BC between the Thebans and Boeotians on one side and the Spartans on the other. The battle took place after the end of the Corinthian War and was thus just another continuation of the recurring battles. The battle itself took place near the village of Leuktra, located in the territory of Thespia.
This battle erupted after a coalition of Boeotian city states called on Sparta to free them from Theban rule and grant them autonomy. The Spartans (led by King Cleombrotos I) invaded Boeotia from Phocis, but did so stealthily across the border mountains, catching the Thebans by surprise enough to capture the fortress of Kreusis, where twelve Theban warships were moored. The Spartan forces numbered between 10,000 and 11,000 men. By contrast, the Thebans, led by EpameinÃ³ndÃ¡s, had only 6,000 to 7,000 men.
The village of Leuktra was chosen for the actual clash. During the battle, there were a number of clashes whether cavalry or mercenary peltasts. The key event, however, was that the Spartans gathered their heavy infantry into a single mass of soldiers, eight to twelve ranks deep. This formation was considered ideal both through the width of the battlefield and the sheer strength of the army. Interestingly, commanders placed their most experienced warriors on the right flank (the most vulnerable and also the most honorable place in the battle lineup). On the other hand, the weaker or less skilled soldiers were placed on the left wing.
Despite this practice, EpameinÃ³ndÃ¡s kept his cavalry together and placed the Theban infantry on his left flank in a line fifty ranks deep, while leaving the center and weaker right flank withdrawn. Once the clash occurred, the Greek wing, 12 ranks deep, could not withstand the onslaught of 50 Theban ranks. Not even the experienced Spartan warriors could do so, and so this wing was crushed before the remaining armies could get into the actual clash. Once the rest of the Spartan army saw the fall of its powerful wing, including its king Cleombrotus, it decided to retreat. The Thebans then abandoned further attacks against the surviving Spartans.
The Battle of Leukter was significant in that it permanently shifted the balance of power in Greece, with Sparta losing its invincibility and being relegated to the role of a second-rate power.
This battle was also crucial in terms of military tactics, through the use of the phalanx (the staggered deployment of infantry). It is highly likely that if the Thebans had been outnumbered, this tactic might not have been used. There were many more years since the use of this technique, and similar manoeuvres were used. Philip II was also influenced by this tactic. Macedon, who was a prisoner of Thebes at the time. His son Alexander the Great perfected the art.