Their reaction reflects a rivalry between Ephraim and Manasseh (Gideon’s tribe) that went right back to the time of their father Joseph. That is in Genesis 48:1–22, where grandfather Jacob switched the blessing by crossing his arms to give the primary blessing to the younger Ephraim over the older Manasseh. And Ephraim did indeed bear a prominent place in the history of the conquest of the Promised Land. Ephraim’s land was central. God had made this tribe significant. So now they feel slighted.
1 Then the men of Ephraim said to him, “What is this that you have done to us, not to call us when you went to fight against Midian?” And they accused him fiercely.