Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

96. Thus spoke Hippocrates, and had gone over half the army, not having had time for more,¹ when the Boeotians (to whom Pagondas just before engaging had been making a second short exhortation) raised the paean, and came down upon them from the hill. The Athenians hastened forward, and the two armies met at a run. [2] The extreme right and left of either army never engaged, for the same reason; they were both prevented by water-courses. But the rest closed, and there was a fierce struggle and pushing of shield against shield. [3] The left wing of the Boeotians as far as their centre was worsted by the Athenians, who pressed hard upon this part of the army, especially upon the Thespians. For the troops ranged at their side having given way they were surrounded and hemmed in; and so the Thespians who perished were cut down fighting hand to hand. [4] Some of the Athenians themselves in surrounding the enemy were thrown into confusion and unwittingly slew one another. On this side then the Boeotians were overcome, and fled to that part of the army which was still fighting; [5] but the right wing, where the Thebans were stationed, overcame the Athenians, and forcing them back, at first step by step, were following hard upon them, when Pagondas, seeing that his left wing was in distress, sent two squadrons of horse unperceived round the hill. [6] They suddenly appeared over the ridge; the victorious wing of the Athenians, fancying that another army was attacking them, was struck with panic; [7] and so at both points, partly owing to this diversion, and partly to the pressure of the advancing Thebans who broke their line, the rout of the Athenian army became general. [8] Some fled to the sea at Delium, others towards Oropus, others to Mount Parnes, or in any direction which gave hope of safety. The Boeotians, especially their cavalry and that of the Locrians which arrived when the rout had begun, pursued and slaughtered them. [9] Night closed upon the pursuit, and aided the mass of the fugitives in their escape. On the next day those of them who had reached Oropus and Delium, which, though defeated, they still held, were conveyed home by sea.