What does Judges 20:31 mean?
Despite outnumbering defenders by fifteen-to-one, eleven of the tribes of Israel have been thoroughly thwarted in two attempts to take the city of Gibeah from the twelfth tribe, Benjamin. The city's natural defenses likely made it especially difficult to attack. The much smaller Benjaminite forces held their ground and devastated those who came near: about one out of every eleven attackers from the original Israeli army has been killed. What might have been a brute-force strategy of attacking the town head on has failed miserably (Judges 20:19–25).This third attempt will be different. Israel will execute a new strategy, further bolstered by God's promise that they will win in this third attack (Judges 20:26–28).
Israel has set men along the same battle lines used in prior attacks. This time, though, they have hidden another part of their army around the city. Those hidden men are ready to spring an ambush when the time is right. Israel initiates the attack in the same manner as the first two attempts. Benjamin's forces come out to engage them, as they did before. Israel's soldiers begin to fall back, as if they are losing ground. They move back along the roadways, including one from Gibeah to Bethel.
The fierce fighters of Benjamin see this as an opportunity, but don't realize it's a trap. They are drawn away from the safety of the city. They succeed in killing about thirty Israelite soldiers along the road and in the open fields as they chase their attackers down. They don't know that Israel has used these men as bait to draw Benjamin's forces further away from town.