Charles Ellicott Commentary Judges 11:27

"I therefore have not sinned against thee, but thou doest me wrong to war against me: Jehovah, the Judge, be judge this day between the children of Israel and the children of Ammon." — Judges 11:27 (ASV)

The Lord the Judge be judge this day. — This is an appeal to the judgment of Jehovah to decide on the justice of an appeal to arms. (Genesis 31:53; Genesis 18:25; 1 Samuel 24:15.)

These verses contain a deeply interesting example of what may be called ancient diplomacy, which is very powerful and straightforward — at once honest, conciliatory, and firm.

Jephthah maintains the rights of Israel on three grounds:

1. Right of direct conquest, not from Ammon but from the Amorites (Judges 11:15–20);
2. The decision of God (Judges 11:21–23), which he supports by an argumentum ad hominem — namely, the acquiescence in this decision of the Moabite god Chemosh (Judges 11:24);
3. Undisputed possession from the first (Judges 11:25–26).

He ends by an appeal to God to approve the justice of his cause.