Joshua 21:43-45 - Albert Barnes' Notes on the Bible

There is no real inconsistency between the declarations of these verses and the fact that the Israelites had not as yet possessed themselves of all the cities allotted to the various tribes Judges 1:21-36 - nor did at any time, subdue the whole extent of country promised to them Numbers 34:1-12. God had fulfilled all His part of the covenant. It was no part of His purpose that the native population should be annihilated suddenly Deuteronomy 7:22; but they were delivered into the hand of Israel, and their complete dispossession could have been effected at any time by that divine aid which was never wanting when sought. At the time referred to in the text, the Canaanites were discouraged, broken in strength, holding fast in isolated spots only up and down the land in the very midst of the tribes of God’s people. The conquest of Canaan was already “ex parte Dei” a perfect work; just as in the New Testament the triumph of the individual Christian and of the Christian Church in their warfare is often spoken of as accomplished in view of the divine will that it should be so, and of divine grace that it may be so. It was therefore, only the inertness and pusillanimity of the Israelites which prevented the completion of the conquest when the allotment of Canaan was made by Joshua; as it was their subsequent backslidings which caused God to turn the tide of victory against them and even to cast them out of the land promised to their forefathers and actually won in the campaigns of Joshua. See the introduction to the Book of Joshua.