Judges 11:8

‘ And the elders of Gilead said to Jephthah, “This is the reason that we are now turned again to you, that you may go with us and fight against the children of Ammon. And you shall be our head over all the inhabitants of Gilead.” '

The elders frankly and humbly replied that the reason they had come was so that he would fight for them and lead them against the children of Ammon. In return they would offer him the headship of the people who had rejected him. This had not been their first intention but they now recognised that it was necessary. It was a big step, for strictly he had no right to be recognised as a true Israelite, never mind their head.