What does Judges 11:22 mean?

This lays out the borders of the disputed territory of Gilead. This is the region which the Ammonite army is preparing to attack. Their intent is to take this land from Israel (Judges 10:17–18; 11:4). Gilead prepared by making Jephthah their leader (Judges 11:4–11). When he confronted the king of Ammon about the impending invasion, he was given a curious response. The enemy king claimed Israel took the territory from them centuries earlier, during the time of Moses (Judges 11:12–13).

In response, Jephthah has sent a history lesson to the king (Judges 11:14–21). He has noted that the original inhabitants of the land were Amorites, not Ammonites. Further, these Amorites had attacked Israel without provocation. Since it was the Lord who gave Israel victory over the Amorites, at that time, it was God who gave the land to Israel. He also notes, later (Judges 11:26), that since the area was conquered its ownership has not been in dispute.

Jephthah defines the borders of Gilead since Moses' era as stretching from the Arnon River in the south to the Jabbok River in the north. It runs from the Jordan River east to the beginning of the region known simply as "the wilderness." The Ammonites possessed a territory of land in the wilderness, but they wanted to take from Israel all the land up to the Jordan River and some distance beyond.