Then Jephthah gathered together all the men of Gilead, and fought with Ephraim; and the men of Gilead struck Ephraim, because they said, You are fugitives of Ephraim, you Gileadites, in the midst of Ephraim, [and] in the midst of Manasseh.
The Ephraimites were the Gileadites’ neighbors to the west. They resented the fact that Jephthah had not requested their assistance in the war with the Ammonites. We noted earlier that the Ephraimites considered themselves superior to their brethren in some respects (cf. Judges 8:1). They foolishly threatened to punish Jephthah for this affront (Judges 12:1).