from Mount Halak, that goes up to Seir, even to Baal Gad in the valley of Lebanon under Mount Hermon: and all their kings he took, and struck them, and put them to death.
The words of God to Moses to which the writer alluded (Joshua 11:23) are probably those in Exodus 23:27-33 (cf. Deuteronomy 7:22). There God told Moses He would not drive all the Canaanites out of the land in one year but little by little. This is how the conquest of the land had advanced thus far and how it should have continued to its completion.