Gideon sent messengers throughout all the hill-country of Ephraim, saying, Come down against Midian, and take before them the waters, as far as Beth Barah, even the Jordan. So all the men of Ephraim were gathered together, and took the waters as far as Beth Barah, even the Jordan.
"Ephraim ... took the waters ... even the Jordan"  (Judges 7:24).  The powerful tribe of Ephraim was here solicited to join in the campaign against Midian, and they promptly responded.  By some chance or oversight Gideon had not solicited their aid until this event; and that was to cause a complaint discussed later in  Judges 8.  Gideon's diplomacy solved the problem satisfactorily.