What does Judges 20:29 mean?

God assured the Israelites they will defeat Gibeah in their third attack (Judges 20:19–28). Since the full tribe of Benjamin is defending Gibeah (Judges 19:14), this means the Israelites will overcome their brothers in that tribe, as well.

Exact maneuvers of the previous two attacks were not described. Here, however, Israel seems to employ a new strategy. They position parts of their army in hiding around the city to ambush the Benjaminites. This appears to be connected to a classic feint, a tactic meant to incite a response which can then be exploited. Israel will draw the Benjaminite fighters out from Gibeah, then attack the city when the bulk of the army of Benjamin is too far away to protect it (Judges 20:30–31).