Mizpah was the place where Jephthah had been solemnly installed—with stipulations—as the military leader in the present war against the Ammonites (Judges 11:11). The name Mizpah means a station or place from which watch can be kept; something like a watchtower. It probably had military importance.
29 Then the Spirit of the LORD was upon Jephthah, and he passed through Gilead and Manasseh and passed on to Mizpah of Gilead, and from Mizpah of Gilead he passed on to the Ammonites.