The city that is in the midst of the river; of which See Poole on "Deuteronomy 3:16", and See Poole on "Joshua 12:2". Either this is the same city now mentioned, even Aroer, which is said to have been a double city, as the very name seems to import, whereof one part was on the bank of the river, and the other in the middle of it, whence we read of the cities of Aroer, Isaiah 17:2; or it is another city, possibly Ar, as it is elsewhere named. Medeba and Dibon; two cities anciently belonging to the Moabites, and taken from them by the Amorites, Numbers 21:30, and from them by the Israelites; and after the Israelites were gone into captivity, recovered by the first possessors the Moabites, as may seem from Isaiah 15:2.
Related Commentaries of Joshua 13:9
Joshua 13:9
9 From Aroer, that is upon the bank of the river Arnon, and the city that is in the midst of the river, and all the plain of Medeba unto Dibon;