All at first favored them. The outwork was abandoned by its garrison, and the Athenian engineers began to dismantle it. In vain Gylippus brought up fresh troops to check the assault; the Athenians broke and drove them back, and continued to press hotly forward, in the full confidence of victory. But, amid the general consternation of the Syracusans and their confederates, one body of infantry stood firm. This was a brigade of their Boeotian allies, which was posted low down the slope of Epipolae, outside the city walls. Coolly and steadily the Boeotian infantry formed their line, and, undismayed by the current of flight around them, advanced against the advancing Athenians. This was the crisis of the battle. But the Athenian van was disorganized by its own previous successes; and, yielding to the unexpected charge thus made on it by troops in perfect order, and of the most obstinate courage, it was driven back in confusion upon the other divisions of the army that still continued to press forward. When once the tide was thus turned, the Syracusans passed rapidly from the extreme of panic to the extreme of vengeful daring, and with all their forces they now fiercely assailed the embarrassed and receding Athenians. In vain did the officers of the latter strive to reform their line. Amid the din and the shouting of the fight, and the confusion inseparable upon a night engagement, especially one where many thousand combatants were pent and whirled together in a narrow and uneven area, the necessary manoeuvres were impracticable; and though many companies still fought on desperately, wherever the moonlight showed them the semblance of a foe, they fought without concert or subordination; and not infrequently, amid the deadly chaos, Athenian troops assailed each other. Keeping their ranks close, the Syracusans and their allies pressed on against the disorganized masses of the besiegers, and at length drove them, with heavy slaughter, over the cliffs, which an hour or two before they had scaled full of hope and apparently certain of success. This defeat was decisive of the event of the siege. The Athenians afterward struggled only to protect themselves from the vengeance which the Syracusans sought to wreak in the complete destruction of their invaders. Never, however, was vengeance more complete and terrible. A series of sea-fights followed, in which the Athenian galleys were utterly destroyed or captured. The mariners and soldiers who escaped death in disastrous engagements, and a vain attempt to force a retreat into the interior of the island, became prisoners of war. Nicias and Demosthenes were put to death in cold blood, and their men either perished miserably in the Syracusan dungeons or were sold into slavery to the very persons whom, in their pride of power, they had crossed the seas to enslave.