Judges 20:44

And there fell of Benjamin eighteen thousand men
Just the number they had slain of Israel in the second battle. This is the number of them that were slain when Israel turned upon them, and by that time they got to the east of Gibeah; afterwards 5000 more were slain on the highways, and 2000 near Gidom, as after related:

all these were men of valour;
as appears by three times facing and engaging with the army of Israel, so vastly superior to them, and twice beating them.