The Theban-Spartan War or Boeotian War (379-371 BC) was a conflict triggered by Sparta's attempts to impose her dominance over the rest of Greece, and that ended with a dramatic Spartan defeat that marked the beginning of the end for Sparta as a great power.
Background to the War
Although Sparta had always had an impressive military reputation, that only translated into power outside the Peloponnese after her victory in the Great Peloponnesian War in 404 BC. This temporarily eliminated Athens as a great power, and left Sparta as a major land and naval power. The Spartans soon managed to alienate their allies from the Peloponnesian War. Within Greece they denied their allies many spoils of the victory, while further afield they supported Cyrus the Younger's revolt against Artaxerxes II of Persia. This triggered the Persian-Spartan War (400-387 BC), which in turn helped convince Sparta's Greek rivals that she was vulnerable to attack. The Thebans managed to incite a border incident between Locris and Phocis, their western neighbours, and Sparta soon found herself dragged into the conflict (Corinthian War, 395-386 BC). Athens and Corinth entered the war on the Theban side. The Spartans won the major land battles of the war, although didn't manage to win any truly decisive victories. At sea their fleet was defeated by a joint Persian-Greek fleet at Cnidus (394 BC), and their maritime empire around the Aegean collapsed. The revival of Athenian power then began to worry the Persians. They made peace with Sparta, and between them the two powers were able to impose the King's Peace, or Peace of Antalcides, on the other Greek powers.
Relations between Sparta and Thebes were strained by the terms of the King's Peace, which guaranteed the autonomy of the Greek cities. Sparta interpreted this as meaning the Boeotian League would have to be dismantled. In contrast Sparta's own Peloponnesian League was allowed to continue. Their reputation was also damaged by their willingness to hand the Greeks of Asia Minor over to the Persians.
The strains between Sparta and Thebes turned into a crisis in 382 when a Spartan army, led by Phoebidas, passing through Thebes on its way to campaign in Chalcidice, captured the Cadmea, the citadel of Thebes and then imposed a new government on the city (possibly with the support of a pro-Spartan faction within the city). After carrying out this coup the Spartans continued on their way north, eventually capturing Olynthus in 379. It isn't clear if the coup at Thebes was carried out on Phoebidas's own authority, or with the support of King Agesilaus II of Sparta. Phoebidas was fined and removed from command of the northern expedition, but later returned to favour. In the aftermath of his actions a Spartan garrison remained in the Cadmea, and the pro-Spartan Leontiades was left in charge of Thebes.
Outbreak of the War
In December 379 the Theban exiles, including Epaminondas and Pelopidas (the 'Liberators'), rose against the Spartans and their supporters. They then attacked the garrison on the Cadmea and forced it to surrender on terms. Leontiades was captured and killed. A small Athenian force took part in the uprising, but at first the new Theban government hoped to stay on good terms with the Spartans. Instead Sparta sent an army under King Cleombrotus into Boeotian. He defeated the Theban border guards, but then stalled south-west of Thebes, before deciding to return to Sparta. He left a smaller force under the harmost Sphodrias at Thespiae. Sphodrias then made a crucial mistake. The two Athenian generals who had taken part in the fighting at Thebes had been put on trial, one was executed and the other was exiled. Despite this demonstration of good faith Sphodrias decided to try and launch a surprise attack on the Piraeus (possibly with the encouragement of the new Theban leadership, determined to prevent Athens and Sparta from forming an alliance). His attempt at a night march badly misfired and he ended up isolated in the area east of Eleusis and fourteen miles away from his target. He was forced to withdraw without achieving anything. The Athenians didn't immediately declare war, but Sphodrias had Royal support and although he was put on trial, he was acquitted.
In 378 Athens and the newly freed Thebes agreed a defensive alliance. King Agesilaus led another Spartan army to Thebes, but once again the Spartans were unable to retake the city. The Thebans had built a series of defensive fortifications to protect their most valuable land, but Agesilaus was able to get inside these walls and threaten Thebes. The city was defended by a combined Athenian and Theban army that took up a strong position on a hill near the city. The Athenian contingent was commanded by Chabrias, one of their most successful commanders of this period. He ordered his men to take up a defensive position, kneeling behind their shields. This display of confidence helped convince Agesilaus not to attack, and he withdrew after ravaging the local areas. The Spartans then suffered a second setback when Phoebidas, their commander at Thespiae, was defeated and killed while chasing a raiding party.
The Spartan failures in 378 attracted new partners to the anti-Spartan alliance. Byzantium, Lesbos and Rhodes all formed alliances with Athens during the year and many parts of former Boeotian League abandoned the Spartan cause and joined a new more democratic Boeotian Confederacy.
Early in 377 the new alliances were turned into a formal Second Athenian League. The Delian League had soon turned into an Athenian Empire, so this new league was designed to prevent that. Each member was guaranteed its autonomy (also making sure that it didn’t break the terms of the King's Peace). The league had a council, in which each state had one vote. No foreign garrisons were to be imposed. Each state made a contribution to the central funds. This league lasted for 40 years, and was only dissolved after Philip of Macedonia's victory at Chaeronea.
The league had a number of able leaders, including the Athenian generals Iphicrates and Chabrias and the admiral Timotheus, son of Colon, and the Theban Epaminondas.
In 377 Agesilaus led a second invasion of Boeotia. Once again he was able to slip past the Theban defenders, but once again he was unable to take the city. He did ravage the fields for a second time, forcing the Thebans to try and buy grain from Thessaly. The two triremes sent to buy the grain were captured as they passed Hestiaea on Euboea, but escaped from their prison and triggered a revolt in Hestiaea before continuing with their mission. Towards the end of the year Agesilaus suffered a ruptured vein in on leg, and had to relinquish command.
The invasion of 376 was thus commanded by King Cleombrotus. This time the Spartans were unable to cross the Cithaeron range, and no invasion of Boeotian took place. The Spartans then changed strategy, and raised a fresh fleet with which they attempted to blockade Athens. The Athenians responding by raising a powerful fleet of their own, which they then sent to besiege Naxos in an attempt to keep the grain routes open. The Spartans sent a smaller fleet under the command of Pollis to try and raise the siege, but he was defeated in killed in a naval battle off Naxos by the Athenian leader Chabrias. This was the first independent Athenian naval victory since the end of the Great Peloponnesian War. Later in the same year Chabrias may have raided Laconia, and possibly reached Sellasia, to the north-east of Sparta.
In 375 most of the fighting was in the area to the west of Thebes. The failure of the Spartan invasion of 376 had allowed the Thebans to win over most of Boeotia, even eliminating the Spartan stronghold at Thespiae. Plataea and Orchomenus remained under Spartan dominance. The Spartans decided to try and send a fleet across the Corinthian Gulf to restore the situation. The allies responded by moving an Athenian fleet around the Peloponnese to the western end of the Gulf. This fleet, under the command of Timotheus, son of the successful naval commander Conon, defeated the Spartan navarch Nicolochus at Alyzeia in the summer of 375, and won over a number of allies in the area. The Spartans also suffered a setback on land. Pelopidas, one of the Liberators, attempted to take advantage of the absence of the Spartan garrison of Orchomenus, but this attack failed. During the return journey he was attacked by the Spartans, and inflicted a defeat on them at Tegyra, killing the two Spartan polemarchs Gorgoleon and Theopompus. Although this didn’t alter the balance of power at Orchomenus, it was very good for Allied morale.
In late 375 or early 374 Sparta and Athens made peace. Sparta recognised the Athenian League and Athens recognised Sparta's dominance in the Peloponnese. This peace didn't last for long.
Tension continued to be high, and in 373/2 the navarch Mnassipus was sent west to capture Corcyra (Corfu). The city of Corcyra was besieged and the locals called for help from Athens. Athens responded by sending six peltasts overland and organising a fleet of sixty ships, eventually commanded by Iphicrates, a successful general during the Corinthian War. Back on Corcyra the Spartan siege became lax and the defenders launched a sortie in which Mnassipus was killed. The Spartans rallied at their camp, but abandoned the siege when news arrived that Iphicrates was close by.
End of the War
The Thebans took advantage of the renewal of the conflict to capture and destroy Plataea and destroy the walls of Thespiae. They were now beginning to worry their Athenian allies, and a new peace conference was held at Sparta. Representatives from the Greek states, Dionysius of Syracuse, Amyntas III, king of Macedonia and Artaxerxes of Persia were all present, and a peace treaty was agreed in which each side agreed to withdraw their governors and garrisons from other cities, and respect the autonomy of all cities.
There are differing accounts of the end of this peace conference. According to Xenophon the Thebans returned to the negotiating table on the day after the treaty had been agreed, and asked to be allowed to sign for the entire Boeotian Confederacy. Agesilaus refused to accept these terms, and struck Thebes off the list of signatories. Despite this last minute hitch the peace went into effect for every other power, leaving just Thebes and Sparta at war.
The Spartans reacted by sending an army under King Cleombrotus to invade Boeotia. At the battle of Leuctra (371) the Thebans inflicted a crushing defeat on this army, the first major defeat ever suffered by the Spartan infantry in a full sized open battle. King Cleombrotus was killed in the battle, along with 400 full Spartiates. The battle of Leuctra permanently changed the political balance in Greece. In the aftermath the Peloponnesian League fell apart, leaving Sparta standing almost alone. The Athenian League expanded rapidly, while the Boeotian League became an effective force. The decade after Leuctra was dominated by the war of the Theban Hegemony, and in particular by a series of successful invasions of the Peloponnese in which the opportunity to weaken Sparta created by the battle of Leuctra was turned into reality.