The LORD helped us capture every town from the Arnon River gorge north to the boundary of Gilead, including the town of Aroer on the edge of the gorge and the town in the middle of the gorge.
This region stretched north from the town in the middle of the Arnon River valley, and included the town of Aroer on the northern edge of the valley. It covered the flatlands of Medeba north of Dibon,
A little later, the Israelites set out into the desert, going east of Edom and Moab, and camping on the eastern side of the Arnon River gorge. The Arnon is the eastern border of Moab, and since the Israelites didn't cross it, they didn't even set foot in Moab.