What does Judges 20:19 mean?

Eleven of Israel's twelve tribes have been outraged by the reports of atrocities done in Gibeah. This city of the tribe of Benjamin (Judges 19:14) tolerated the heinous rape and murder of travelers by a frenzied mob (Judges 19:22–28). Israel's response was to send a massive collection of troops and demand the guilty men be handed over (Judges 20:12–13). Instead of cooperating with their fellow Israelites, the Benjaminites decided to defend their territory. They have amassed their own army, including several hundred specially trained stone slingers. Yet their army is only about one-fifteenth the size of their attackers (Judges 20:15–17).

When Benjamin rejected the demands of Israel, the eleven tribes sought God's direction for who would attack first (Judges 20:18). The fighters of the tribe of Judah position themselves to attack Gibeah, as the Lord has directed them. The time for discussion has passed, and war is imminent.