The plan would doubtless have succeeded, since only a small number of the citizens had remained behind, had not Agesilaus, hearing of the project from a deserter, despatched a messenger to his son Archidamus, with the command immediately to put the town in a state of defence, while he himself at once set out to return with the cavalry. Thus when Epaminondas approached the banks of the Eurotas, almost at the same time as Agesilaus, he found the town so well watched and guarded that, after a hotly contested battle, he was obliged to retreat with loss. It is true that he managed to penetrate to the market-place, but when he attempted to storm the upper parts of the town, he encountered an obstinate resistance. The inhabitants had torn down their houses and thrown up barricades to bar the approaches. Protected by these dispositions and filled with patriotic enthusiasm, the Spartan citizenhood under the guidance of the old king and his son performed prodigies of valour, and gave evidence, as Xenophon says, that no one can easily maintain his ground against despairing men. Even women and children did their part by hurling down stones, utensils, and missiles from the roofs. Isadas, the handsome son of Phœbidas, specially distinguished himself by his heroism and his bold courage. Disappointed in his expectation of surprising Sparta undefended, Epaminondas desisted from the attack, the more readily when he learned that the whole united army of the enemy had started from Mantinea and was hastening to the assistance of the beleaguered town.
He now formed a plan to make up for the failure of the undertaking against Sparta by seizing the town of Mantinea, now denuded of its troops, or at least to make spoil of the stores of grain and herds of cattle collected there. Deceiving the enemy by means of watchfires and a simulated attack, he led the army back to Tegea by a difficult night march. Here he accorded a brief rest to the wearied infantry, whilst the mounted troops proceeded towards Mantinea. But Epaminondas now learned that fate was against him. The Thebans had already advanced to within seven stadia [nearly a mile] of the town, when they saw the Athenian auxiliaries entering the gates from the opposite side. Hegesilaus, the leader of the Athenian cavalry, was assailed by the prayers of the Mantineans, in alarm for their property; and he at once marched against the enemy, to whom he gave battle under the walls of the town, in a sharp cavalry action, from which the Athenians eventually retired victorious. In this preliminary skirmish at Mantinea fell the brave Athenian leaders, Cephisodorus, and Gryllus, the son of Xenophon. Their memory continued to be held in honour by their fellow-citizens. Gryllus was represented by the painter Euphron in the act of slaying a Theban with his spear, and this circumstance, by a confusion of the previous encounter with the main battle, may have given rise to the story that Epaminondas was slain by Gryllus.
The whole forces of both sides now concentrated in the plain of Mantinea and Tegea, determined to settle the future destiny of Greece by a decisive battle. Epaminondas had pressing reasons for desiring this settlement. The two unsuccessful enterprises, with the strenuous and fruitless marches, were not calculated to enhance his reputation as a general; while a long delay would necessarily weaken the spirit of his soldiers, who adhered to him with such great devotion, and would undermine the prestige of Thebes. Moreover his followers were superior in number to those of the adversary. The size of his army is set down at thirty thousand heavy-armed troops and three thousand cavalry; the enemy’s force was smaller by ten thousand hoplites and one thousand mounted men. Faith in Epaminondas had inspired his soldiers with the greatest enthusiasm for the conflict; they eagerly polished their helmets and shields and sharpened their swords and lances, while the Arcadian club-men assumed the Theban ensign.
In the disposition and order of his line of battle, Epaminondas followed much the same plan which had been found to answer so well at Leuctra, only that in order to deceive and make sure of the foe, he caused the troops ranged for the conflict to make a feint of retreating towards the western heights; then, when the enemy, fancying that the encounter would be delayed, began to break up their order of battle, he suddenly made a rapid and vehement attack, so that at the first onset his left wing, where the Thebans and the bravest of the allies had their place, broke the enemy’s left, composed of the Spartans and Mantineans. Already the whole wing had begun to waver and plunge into a confused flight; when, at the very moment that he was about to win a complete victory, Epaminondas, pressing boldly forward, was struck in the breast by a spear thrown from the hostile ranks, and with such force that the shaft broke off and the iron remained fixed in the wound.