Peter Pett's Commentary on the Bible
Judges 20 - Introduction
Chapter 20. The Response.
In this chapter the Levite's appeal to the tribal confederacy of Israel is answered. The case is heard and the children of Benjamin are commanded to deliver the wrongdoers for punishment in accordance with the law and the covenant. Their refusal to do so is a breach of covenant which the others see as bringing God's wrath on themselves unless they do something about it. Thus they seek to put pressure on them to do so.
When this also is rejected they go in to do it themselves. In order, in their view, to avoid the wrath of God, the tribal confederacy seek to enforce their decree. This results in a tribal war which is evidence of a serious breach of covenant on behalf of ‘Benjamin', and eventually, after two setbacks, they defeat the children of Benjamin with God's backing, and exact the vengeance which tradition required, the near extermination of Benjamin.