The decade between the Persian Wars and the great Peloponnesian War was a restless one. Alliances formed and dissolved, leagues swelled and fractured, and full-scale war was rare even as tension never quite eased. By 457 BC, Athens, leader of the Delian League, had collided with Corinth and its powerful ally Sparta over the strategic town of Megara. The flashpoint came at Tanagra, where the Athenians fielded some 14,000 men and lost. Yet Sparta's victory rang hollow. The Spartans had bled so badly in winning that they could not press their advantage, and they withdrew home across the Isthmus, leaving Boeotia undefended. Into that vacuum the Athenians poured their reorganized army.

Command fell to Myronides, an Athenian general whose name would be remembered for this single, decisive stroke. He led his men into Boeotia and met the assembled Boeotian forces at Oenophyta, in the country east of Thebes. The clash was a hoplite battle in the classic mold, lines of bronze-clad citizen-soldiers pushing against one another until one side broke. The Boeotians broke. With the field won, the Athenians did not pause to celebrate. They marched on, tore down the walls of Tanagra, the very town where they had so recently been defeated, and pushed deeper still, ravaging the lands of Locris and Phocis to the northwest.

One battle rarely decides a war, but Oenophyta came close. The victory gave Athens mastery over central Greece, ushering in roughly a decade in which Boeotia, Locris, and Phocis all fell under Athenian sway. The consequences cascaded outward fast. The island of Aegina, long a thorn in Athens' side, surrendered soon after. And in the same stretch of confidence, Athens completed the Long Walls that joined the city to its port at Piraeus, fortifications Sparta had openly opposed, sealing Athens into an impregnable corridor between citadel and sea. For a brief, brilliant span, Athenian power reached its widest land extent.

Stand in this corner of Boeotia today and there is little to mark the slaughter, only quiet fields, low hills, and the slow line of the Asopus river that has watered this plain since before the Greeks counted their years. The exact site of Oenophyta has been argued over by scholars, its memory preserved less in stone than in the terse pages of Thucydides, who recorded the campaign in a few unsentimental lines. Yet the men who fell here, Athenian and Boeotian alike, were citizens fighting for cities they believed eternal. The Athenian supremacy they won would not last; within a decade Boeotia rose again and threw it off. Empires, like the harvests of this plain, are seasonal.