The river-gorge running west into the Dead Sea that forms the border between Moab and the Amorites — a fact Numbers 21:13 stops the narrative to state, and then the chapter’s whole war is fought over. Today it is the Wadi al-Mujib, a canyon over a kilometre across and some seven hundred metres deep where it meets the sea; it is the reason a boundary here is not a line on a map but a physical fact. ⚠ The Arnon is also the northern limit named in the quoted war-poetry of vv14-15 and in the Heshbon ballad of vv27-30, and it reappears on the ninth-century Mesha Stele, where Moab’s own king records building the highway across it.