Albert Barnes Commentary Judges 12:2

"And Jephthah said unto them, I and my people were at great strife with the children of Ammon; and when I called you, ye saved me not out of their hand." — Judges 12:2 (ASV)

When I called you ... - This circumstance is not related in the main narrative. It is likely to have occurred when Jephthah was first chosen leader by the Gileadites, and when Ephraim would probably ignore his claims.