Albert Barnes Commentary Judges 8:10

"Now Zebah and Zalmunna were in Karkor, and their hosts with them, about fifteen thousand men, all that were left of all the host of the children of the east; for there fell a hundred and twenty thousand men that drew sword." — Judges 8:10 (ASV)

Zebah and Zalmunna seem to have fled nearly due east to Karkor, which was probably an enclosure of some kind (perhaps a walled sheepfold, compare Numbers 31:32 note). Its site is unknown; but it was near Nobah, in the half-tribe of Manasseh in Gilead (Numbers 32:40), and Jogbehah was in the tribe of Gad (Numbers 32:34–35). Gideon, perhaps taking a circuit so as to come upon them from the east, fell suddenly upon them, apparently at night, surprised them, and struck them.