What does Judges 21:6 mean?

The writer of Judges notes that the rest of Israel had compassion for the tribe of Benjamin. They were brokenhearted that the people of Benjamin were so near to extinction, leaving a gap in the twelve tribes of Israel. The words used here are poignant and interesting: Benjamin's tribe is spoken of fondly as a "brother." At the same time, what happened to them is described using a Hebrew word literally meaning "hacked" or "chopped." Of course, it was the rage of the eleven tribes, in response to Benjamin's resistance (Judges 20:12–13) which led them to nearly annihilate the entire region (Judges 20:47–48).

It's natural to read this passage with a sense of confusion, or even irritation, at the Israelites' thinking. In eagerness to purge evil, they seem to have taken two hasty oaths. They'd promised God to do seemingly foolish things, then gone well beyond His command to attack the guilty men of Gibeah (Judges 20:27–28). Scripture never indicates God intended them to wipe out every man, woman, and child of Benjamin. The only reason Benjamin has any hope at all is because six hundred men had escaped the slaughter and were hiding in caves. Yet the people have wept while asking, "how did this happen?" (Judges 21:1–3) and seeking a solution.

Now, a second day after the disaster, the eleven tribes are looking for a solution which will allow them to keep their vows, while also sparing the tribe of Benjamin from disappearing (Judges 21:4–5).