Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[160] When therefore they had divided the army into two parts, they laid the one half of them in ambush about the city Gibeah by night, while the other half attacked the Benjamites, who retiring upon the assault, the Benjamites pursued them, while the Hebrews retired by slow degrees, as very desirous to draw them entirely from the city; and the other followed them as they retired, till both the old men and the young men that were left in the city, as too weak to fight, came running out together with them, as willing to bring their enemies under. However, when they were a great way from the city the Hebrews ran away no longer, but turned back to fight them, and lifted up the signal they had agreed on to those that lay in ambush, who rose up, and with a great noise fell upon the enemy. Now, as soon as ever they perceived themselves to be deceived, they knew not what to do; and when they were driven into a certain hollow place which was in a valley, they were shot at by those that encompassed them, till they were all destroyed, excepting six hundred, which formed themselves into a close body of men, and forced their passage through the midst of their enemies, and fled to the neighboring mountains, and, seizing upon them, remained there; but the rest of them, being about twenty-five thousand, were slain. Then did the Israelites burn Gibeah, and slew the women, and the males that were under age; and did the same also to the other cities of the Benjamites; and, indeed, they were enraged to that degree, that they sent twelve thousand men out of the army, and gave them orders to destroy Jabesh Gilead, because it did not join with them in fighting against the Benjamites. Accordingly, those that were sent slew the men of war, with their children and wives, excepting four hundred virgins. To such a degree had they proceeded in their anger, because they not only had the suffering of the Levite's wife to avenge, but the slaughter of their own soldiers.