and ruled over Mount Hermon and Salecah and all Bashan to the boundary of the Geshurites and the Maacathites, and over half of Gilead to the boundary of Sihon king of Heshbon.
Joshua, or whoever else is the historian before he comes to sum up the new conquests Israel had made, in these verses receives their former conquests in Moses's time, under whom they became masters of the great and potent kingdoms of Sihon and Og.
Commenting on Joshua 12:1-6
And reigned in Mount Hermon,.... That is, over all the people that inhabited that mount or dwelt under it, Jos 11:17, and adjacent to it, of which mountain; see Gill on Deu 3:8 and See Gill on Deu 3:9, and in Salcah: which was a city belonging to the kingdom of Og, Deu 3:10, and in all Bashan; or Batanea, a country famous for pasturage...
The border of the Geshurites - The country of Bashan, in the days of Moses and Joshua, extended from the river Jabbok on the south to the frontiers of the Geshurites and Maachathites on the north, to the foot of the mountains of Hermon.