So Joshua took the whole land, according to all that Yahweh spoke to Moses; and Joshua gave it for an inheritance to Israel according to their divisions by their tribes. The land had rest from war.
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.