The Battle of Leuctra was a battle fought on 6 July 371 BC between the Boeotians led by the Thebans, and the Spartans along with their allies amidst the post-Corinthian War conflict. The battle took place in the neighbourhood of Leuctra, a village in Boeotia in the territory of Thespiae. The Theban victory shattered Sparta’s immense influence over the Greek peninsula, which Sparta had gained long before its victory in the Peloponnesian War a generation earlier.
In 371 BC, the newly established democracy of Thebes had elected four Boeotarchs, the traditional title of the generals of the Boeotian League, and so proclaimed their intention of reconstituting the aforementioned league that Sparta had disbanded. During this period, Thebes had had an ally in Athens, but Athens was far from happy with the treatment Plataea had received. When it came to swearing an oath to respect the treaty, Sparta swore on behalf of itself and its allies. When Epaminondas came forward, asking to swear on behalf of the whole Boeotian League, the Spartans refused, saying he could swear as the representative of Thebes or not at all. This Epaminondas refused. (According to Xenophon, the Thebans signed as “the Thebans”, and asked the next day to change their signature to “the Boeotians”, but one of the Spartan kings, Agesilaus II, would not allow it.) In this, Sparta saw an opportunity to reassert its shaky authority in central Greece. Hence, the other Spartan king, Cleombrotus I, marched to war from Phocis.
Rather than take the expected easier route into Boeotia through the usual defile, the Spartans marched over the hills via Thisbae and took the fortress of Creusis (along with twelve Theban warships) before the Thebans were aware of their presence, and then proceeded to Leuctra where they were confronted by the Boeotian army. Initially, the six Boeotian generals present were divided as to whether to offer battle, with Epaminondas being the main advocate in favor of battle. Only when a seventh arrived, who sided with Epaminondas, was the decision made. In spite of inferior numbers and the doubtful loyalty of their allies, the Boeotians would offer battle on the plain before the town.
The battle opened with the Spartans’ mercenary peltasts (slingers, javeliniers, and/or skirmishers) attacking and driving back the Boeotian camp followers and others who were reluctant to fight. According to Xenophon, the Boeotian camp followers were trying to leave the field, as they did not intend to fight; this Spartan action drove them back into the Theban army, inadvertently making the Theban force stronger. There followed a cavalry engagement, in which the Thebans drove their enemies off the field. Initially, the Spartan infantry were sent into disarray when their retreating cavalry hopelessly disrupted Cleombrotus’s attempt to outflank the Theban left column. At this point the Theban left hit the Spartan right with the Sacred Band of Thebes, led by Pelopidas, at its head. The decisive engagement was then fought out between the Theban and Spartan infantry.
The normal practice of the Spartans (and, indeed, the Greeks in general) was to establish their heavily armed infantry in a solid mass, or phalanx, some eight to twelve men deep. This was considered to allow for the best balance between depth (the pushing power it provided) and width (the area of coverage of the phalanx’s front battle line). The infantry would advance together so that the attack flowed unbroken against their enemy.
In a major break with tradition, Epaminondas massed his cavalry and a fifty-deep column of Theban infantry on his left wing, and sent forward this body against the Spartan right. His shallower and weaker center and right wing columns were drawn up so that they were progressively further to the right and rear of the proceeding column, in the so-called Echelon formation. The Theban center and right were held back, screened by skirmishers and cavalry. The infantry engaged, and the Thebans smashed the Spartan right wing. The Spartans’ twelve-deep formation on their right wing could not sustain the heavy impact of their opponents’ 50-deep column. The Spartan right was hurled back with a loss of about 1,000 men, of whom 400 were some of Sparta’s most experienced soldiers, including King Cleombrotus I.
Plutarch describes Pelopidas leading the Band and catching the Spartans in disorder, but there is nothing in his account that conveys anything other than the Sacred Band being the head of the column, and the Spartans were disordered not because they were taken in the flank but because they were caught in mid-maneuver, extending their line.
Seeing their right wing beaten, the rest of the Peloponnesians, who were essentially unwilling participants, retired and left the enemy in possession of the field.
The battle’s political effects were far-reaching: the losses in material strength and prestige (prestige being an inestimably important factor in the Peloponnesian War) sustained by the Spartans at Leuctra and subsequently at the Battle of Mantinea were key in depriving them forever of their supremacy in Greece. Therefore, the battle permanently altered the Greek balance of power, as Sparta was deprived of its former prominence and was reduced to a second-rate power among the Greek city-states.