Albert Barnes Commentary Judges 20:21

"And the children of Benjamin came forth out of Gibeah, and destroyed down to the ground of the Israelites on that day twenty and two thousand men." — Judges 20:21 (ASV)

Gibeah, being on a hill, was difficult of access to an attacking army, and gave great advantage to the defenders, who fought from higher ground, and probably defended a narrow pass, while their companions on the walls could harass the assailants with their slingstones.