The Battle of Leuctra (, ) was fought on 6 July 371 BC between the Boeotians led by the Thebans, and the Spartans along with their allies. The battle occurred in the context of the King's Peace, or Peace of Antalcidas, which had ended the Corinthian War in 386 BC. The Peace was formally renewed in 375 BC, but a disagreement between the Spartans and the Thebans over the protocol for renewing the Peace again in 371 led directly to the battle, which took place in the vicinity of Leuctra, a village in Boeotia in the territory of Thespiae. The mainly Theban victory shattered Sparta's immense influence over the Greek peninsula, and the wider Aegean Greek world, which Sparta had gained with its victory in the Peloponnesian War a generation earlier.

Prelude

The Corinthian War, between Sparta and a Persian-backed coalition of Thebes, Athens, Corinth, Argos and other Greek allies, had ended in 387/6 BC with the King's PeaceThe "King" here referring to the Persian king Artaxerxes II. (also called the Peace of Antalcidas, or the first Common Peace), under the terms of which the autonomy of all Greek cities not under Persian control was guaranteed.Buckler and Beck 2009, pp. 39, 71–72; Hamilton 1997, p. 41; Cartledge 1987, pp. 369–370; Xenophon, Hellenica 5.1.31, 35–36; Diodorus Siculus, 14.110.3–4; Plutarch, Artaxerxes 21.4–5. Sparta, as the guarantor of the King's Peace in Greece, immediately used this autonomy clause to force the Thebes-dominated Boeotian League to disband.Hamilton 1997, p. 53; Buckler and Beck 2009, pp. 72, 87; Cartledge 1987, p. 370; Xenophon, Hellenica 5.1.36. Xenophon calls Sparta the prostatai of the King's Peace, and as Cartledge points out "whether or not the Spartans were officially designated 'guarantors' of the Peace on Persia's behalf (prostatai could mean simply 'champions'), they were certainly its most ardent Greek supporters." In 382 BC, the Spartan general Phoebidas seized Thebes' acropolis, the Cadmea, thereby assisting the pro-Spartan Leontiades and his oligarchic supporters in taking control of Thebes, a clear violation of Theban autonomy.Hamilton 1997, p. 54; Munn 1997, pp. 75–76; Buckler and Beck 2009, pp. 76–77; Cartledge 1987, p. 374; Xenophon, Hellenica 5.4.1.

In late 379 BC, an anti-Spartan Theban exile faction overthrew Leontiades,Hamilton 1997, p. 54; Munn 1997, p. 77; Buckler and Beck 2009, pp. 89–90; Xenophon, Hellenica 5.4.2–12; Plutarch, Pelopidas 8–12; Diodorus Siculus, 15.53.2–3. and immediately signaled their intent to reconstitute the Boeotian League by electing four of the leaders of their revolt as Boeotarchs, the traditional title of the leaders of the Boeotian League.Munn 1997, p. 80; Buckler and Beck 2009, pp. 89–90, 98; Plutarch, Pelopidas 13.1, 14.1. This resulted in the Boeotian War starting in 378 BC, and Sparta's succession of failed attempts to regain control of Thebes and Boeotia.Hamilton 1997, pp. 41, 54; Munn 1997, pp. 78–81.

A short lived peace, was agreed to again in 375 BC, with renewed aggression by Thebes in 373 BC. Throughout the Boeotian War, Thebes had continued to expand its dominance over Boeotia. It captured and severely damaged the Boeotian towns of both Plataea, long an ally of Athens, and Thespiae, and forced their citizens into exile.Buckler 1980, p. 46; Munn 1997, pp. 80–81; Buckler and Beck 2009, pp. 97–98; Xenophon, Hellenica 6.3.1, 6.3.5; Pausanias, 9.1.8. By 371 BC, having engaged in costly naval campaigns, both Sparta and Thebes' ally Athens were ready for peace.Munn 1997, p. 81; Buckler 1980, pp. 47–48. Thebes, faced with the prospect of fighting Sparta alone,Athens had informed Thebes of its intention to make peace with Sparta: Buckler and Beck 2009 , p. 41; Buckler 1980, p. 49; Xenophon, Hellenica 6.3.2. was likewise prepared to agree to a new peace treaty, which, like those of 386 and 375, promised the independence of all Greek cities.Munn 1997, p. 81; Buckler 1980, p. 51; Xenophon, Hellenica 6.3.18. When it came time to sign the new treaty, the Theban ambassadors came forward wishing to sign on behalf of the whole Boeotian League, but the Spartans demanded instead that each Boeotian city sign independently, which the Thebans refused.Munn 1997, p. 81; Buckler and Beck 2009, pp. 41–42; Buckler 1980, pp. 52–54; Xenophon, Hellenica 6.3.19–20; Diodorus Siculus, 11.50.4–5.

With Thebes now isolated, Sparta saw an opportunity to reassert its supremacy in central Greece, and the Spartans immediately sent king Cleombrotus I marching, from his position in Phocis in central Greece, into Boeotia. Rather than take the expected and easier route into Boeotia along the northern side of Mount Helicon, the Spartans instead marched over the hills to the south of Helicon, and then proceeded to Leuctra, where they were confronted by a hastily repositioned Boeotian army.Munn 1997, pp. 81–83; Buckler 1980, pp. 54–61; Xenophon, Hellenica 6.4.1–4; Diodorus Siculus, 15.51, 15.53.1–3.

Force sizes and commanders Several ancient sources give numbers for the sizes of the two armies, but none of these sources gives all the numbers involved, and they nearly all disagree. The general modern consensus is that the Spartan commander King Cleombrotus led approximately 10,000 Peloponnesian infantry, including 700 Spartiates (i.e. full Spartan citizens), and 1,000 cavalry, against 7,000 Boeotian infantry, and 700 cavalry, led overall by the Theban commander Epaminondas, with Pelopidas in command of the elite 300-strong Sacred Band.Dahm 2021, pp. 57–60; Munn 1997, p. 83 (Thebes: "some" 6,000, with the Spartan army "twice as large"); Buckler 1980, pp. 62–63 (Sparta: ~ 9,000–10,000 infantry, 800–1,000 cavalry), p. 55 (Thebes: ~ 7,000 infantry, 600 cavalry).

According to Xenophon, 700 Spartiates fought at Leuctra,Dahm 2021, p. 59; Xenophon, Hellenica 6.4.15. while according to Plutarch, Cleombrotus' Peloponnesian army consisted of 2,000 infantry and 1,000 cavalry.Dahm 2021. p. 59; Plutarch, Pelopidas 20.1. Diodorus Siculus reports that Epaminondas led a force (which included all Thebans of military age) numbering no more than 6,000, to be joined later by a Thessalian force of 1,500 infantry and 500 cavalry.Dahm 2021, p. 60; Diodorus Siculus, 15.52.2, 15.54.5. Other, even later sources give much higher numbers for the Peloponnesians, which are harder to believe. According to Polyaenus, the Peloponnesians numbered 40,000 (against only 6,000 "Thebans"), while Frontinus specifies 24,000 infantry and 1,600 cavalry (against only 3,600 infantry and 400 cavalry).Dahm 2021, pp. 59–60; Polyaenus, 2.3.12; Frontinus, 4.2.6. In any case, the similar force ratios (~ 6.5 to 1), given by Polyaenus and Frontinus, are perhaps meant simply to emphasize the difference in the sizes of the two armies.Dahm 2021, p. 60.

Order of battle

The normal practice of the ancient Greeks was to establish their heavily armed infantry in a solid rectangular mass, or phalanx, composed of long files, several ranks deep. The number of ranks varied, with eight thought to be a common phalanx depth, though other depths are documented.Delbrück 1920, p. 53; Cawkwell 1972, p. 261. Examples include the first Battle of Mantinea (418 BC), where Thucydides says that, "although [the Spartans] had not been all drawn up alike, but as each captain chose, they were generally ranged eight deep" (5.68.3), and the Battle of Delium (424 BC), where he says that the Athenians formed up eight-men deep (4.94.1), while the Thebans formed up twenty-five men deep (4.39.4). According to Xenophon (Hellenica 4.2.18), at the Battle of Nemea (394 BC), the Thebans, "disregarding the sixteen-rank formation", which had apparently been agreed to by the Thebans and the other Greek coalition forces opposing the Spartans, "had made their phalanx exceedingly deep". In order to counter the tendency of the phalanx to drift to the right, Greek commanders traditionally placed their most experienced and highly regarded troops on the right wing, with the entire phalanx usually advancing together.Delbrück 1920, p. 165; Cawkwell 1972, p. 261; Thucydides, 5.71.1.

At Leuctra, Cleombrotus' phalanx consisted of two wings, (according to Xenophon "not more than twelve men deep") with the Spartans on the right, and his allied troops on the left. Cleombrotus himself occupied the traditional king's position between the first and second morai (divisions) of the Spartan wing, accompanied by the Spartan hippeis (an elite infantry force of 300 young men probably in their twenties that constituted the royal bodyguard).Buckler 1980, pp. 62–63; Dahm 2021, pp. 103, 132–133; Xenophon Hellenica 6.4.12. According to Xenophon, Constitution of the Lacedaemonians 13.6, during battle the Spartan king "takes the lead of the first regiment [mora] and wheels to the right, until he is between two regiments and two colonels [polemarchs]". For a discussion of the Spartan hippeis, see: Dahm 2021, pp. 73–74; Figueira 2006, pp. 57–84; Cartledge 1987, pp. 204–205. For the age of its members see: Figueira 2006, pp. 62, 64; Cartledge 1987, p. 204.

Epaminondas also organized his phalanx into two wings, the Thebans comprising one wing, and the rest of the Boeotians the other. However, in a break from tradition, Epaminondas massed his Theban infantry in a very deep column (according to Xenophon, at least fifty shields deep), placing it on the left, directly opposite Cleombrotus and the Spartan right. The other Boeotians were drawn up in a shallower line, progressively further to the right and rear of the proceeding column, in an echelon formation, facing the Spartan allies.Buckler 1980, p. 63; Dahm 2021, p. 103; Xenophon, Hellenica 6.4.12; Diodorus Siculus, 15.55.1–2 (Diodorus describes Epaminondas' order of battle "an unusual disposition of his own"; Plutarch, Pelopidas 23.1. Although the Sacred Band would play a crucial role in the battle, no source reports where (exactly) it was positioned. While not mentioning Leuctra specifically, Plutarch does say that Pelopidas, after the Battle of Tegyra (375 BC), where the Sacred Band had:

This has been interpreted to mean that at Leuctra the Sacred Band was deployed as an independent unit somewhere in front.For a discussion of the position of Pelopidas and his Sacred band, see Buckler and Beck 2009, pp. 112–115. Köchly and Rüstow 1852, argued that the Sacred Band was probably positioned at the rear of the column, a view which fell into disfavor in the nineteen twenties, but was revived by Anderson 1970, pp. 216–217. However, Buckler and Beck, p. 115, conclude that the "most reasonable interpretation of Plutarch’s account is that Pelopidas and the Sacred Band were stationed as a unit at the head of Epaminondas’ wing", a view shared by Dahm 2021, p. 103; Tuplin 1987, p. 84, with n. 43; Buckler 1980, p. 63; Judeich 1927; pp. 195–196; Wolter, 1926, pp. 314–315; and Delbrück 1920, pp. 167–168 (pp. 158–159). Epaminondas's plan was, apparently, to make the outcome depend solely upon an engagement of the Thebans against the Spartans, by sending his Thebans forward, against the Spartans, and refusing (i.e. holding back) his Boeotian allies.Dahm 2021, pp. 103, 105, 114–115; Munn 1997, pp. 83–84; Diodorus Siculus, 15.55.2, Plutarch, Pelopidas 23.1–2. Polyaenus reports that, while rallying his Theban troops:

The battle Accounts of the battle are given by four ancient sources: Xenophon (the only contemporary source), Diodorus Siculus (later first century BC), Plutarch (c. 100 AD), and Pausanias (late second century).Dahm 2021, p. 90; Anderson 1970, p. 198; Xenophon, Hellenica 6.4.4–15; Diodorus Siculus, 15.55–56; Plutarch, Pelopidas 23; Pausanias, 9.13.6–12. The sources are problematic, their accounts are sometimes contradictory, and many particulars of the battle have been the subject of debate among scholars.Dahm 2021, pp. 90–93.

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