Then the Spirit of the Lord ... - This was the sanctification of Jephthah for his office of Judge and savior of God’s people Israel. Compare Judges 6:34; Judges 13:25. The declaration is one of the distinctive marks which stamp this history as a divine history.
The geography is rather obscure, but the sense seems to be that Jephthah first raised all the inhabitants of Mount Gilead; then he crossed the Jabbok into Manasseh, and raised them; then he returned at the head of his new forces to his own camp at Mizpeh to join the troops he had left there; and thence at the head of the whole army marched against the Ammonites, who occupied the southern parts of Gilead.