In the fourth century bc, after victory in the Peloponnesian War, Sparta stood supreme in Greece. Yet the fourth century saw two other developments as well. First was the eclipse and resurgence of Thebes, the city-state that unified the rich region of Boeotia in a federal system. The second was the rebirth of Athenian sea power. Rivalry and tension between Thebes and Sparta resulted in open warfare, and in 371 the Theban army smashed the Spartans at the battle of Leuctra (see chapter 8). This stunning shift in the balance of power drew Athens and Sparta into alliance. The entry of Athens into the war posed to Theban leaders a new and more difficult challenge. Behind their strong walls, relatively invulnerable to siege, the Athenians and their fleet were beyond the reach of the Theban army. Thebes, the leading land power, could defeat Athens only by taking to the sea.

In 366 Thebes voted to build a hundred triremes, a fleet large enough to challenge the Athenian navy. In many ways the Theban experience resembles that of Imperial Germany before World War I. Both powers lacked any significant naval traditions. Both faced the finest fleets of their day, fleets long accustomed to superiority at sea. Both suffered from geographical disadvantages. Although Boeotia is washed by the Corinthian Gulf and the Gulf of Euboea, it lacks good harbors.

In view of these difficulties and obstacles, the Boeotian naval program is perhaps the most mysterious and least understood aspect of the Theban ascendancy.