Then the Spirit of the Lord came upon Jephthah
The spirit of strength, as the Targum; of fortitude of mind, of uncommon valour and courage, and of zeal for God and Israel, and against their enemies; such a spirit as used to be given to men, when they were in an extraordinary manner raised up by the Lord, to be judges, saviours, and deliverers of his people; so that as Jephthah was before chosen by the people to be the general and head of the tribes beyond Jordan, he was raised up and qualified by the Lord now to be the judge of all Israel; of which the Spirit of the Lord coming on him was a sufficient proof and evidence:
and he passed over Gilead and Manasseh;
the countries that belonged to Reuben, Gad, and the half tribe of Manasseh; however, all that part of it which lay from the place where he was, to the land of the children of Ammon:
and passed over Mizpeh of Gilead;
which lay to the north of the land of Gilead, or tribe of Gad:
and from Mizpeh of Gilead he passed over to the children of Ammon;
did not stay for them, to bring on the war in the land of Gilead, but prevented it by carrying it into the land of the children of Ammon. It seems by this, that though the children of Ammon had encamped in Gilead some time before, ( Judges 10:17 ) , yet for some reason or another they had decamped, and had retired into their own country; but yet threatening Israel with a war, and preparing for it.