What does Judges 12:4 mean?
The men of Ephraim have shown up in Gilead ready to do battle (Judges 12:1), after the fight against the Ammonites was already won (Judges 11:32–33). They claim to be furious that Jephthah and the people of Gilead did not include them in their successful war (Judges 12:2–3). Jephthah has responded that Ephraim had many opportunities to help, but never came (Judges 10:17–18; 11:4).Rather than being satisfied with this explanation, the men of Ephraim seem even more angry. They taunt the people of Gilead, calling them "fugitives of Ephraim." They imply the clan of Gilead is living in territory which should belong to Ephraim and Manasseh. This might also be a jab at Jephthah's history as an exile (Judges 11:1–3). Another possible meaning is that Gilead, which is technically part of the tribe of Manasseh, is so intermingled with the people of Ephraim that they have lost identity with either tribe and so the land is open for dispute.
For his part, Jephthah takes the threats of Ephraim seriously. This makes sense, as the tribe arrived armed and ready for battle, effectively invading Gilead and then making threats. Jephthah gathers up the fighters of Gilead once more and attacks the men of Ephraim, striking them hard, as the following verses report (Judges 12:5–7).