psalms 78:9 The children of Ephraim, being armed, and carrying bows, turned back in the day of battle. - Free Bible Online

      9-11. The privileges of the first-born which belonged to Joseph (1Ch 5:1, 2) were assigned to Ephraim by Jacob (Ge 48:1). The supremacy of the tribe thus intimated was recognized by its position (in the marching of the nation to Canaan) next to the ark (Nu 2:18-24), by the selection of the first permanent locality for the ark within its borders at Shiloh, and by the extensive and fertile province given for its possession. Traces of this prominence remained after the schism under Rehoboam, in the use, by later writers, of Ephraim for Israel (compare Ho 5:3-14; 11:3-12). Though a strong, well-armed tribe, and, from an early period, emulous and haughty (compare Jos 17:14; Jud 8:1-3; 2Sa 19:41), it appears, in this place, that it had rather led the rest in cowardice than courage; and had incurred God's displeasure, because, diffident of His promise, though often heretofore fulfilled, it had failed as a leader to carry out the terms of the covenant, by not driving out the heathen (Ex 23:24; De 31:16; 2Ki 17:15).

JFB.