And at that time came Joshua, and cut off the Anakims from the mountains, from Hebron, from Debir, from Anab, and from all the mountains of Judah, and from all the mountains of Israel: Joshua destroyed them utterly with their cities.

Wesley's Notes

11:21 At that time - In that war, but in divers years. The mountain - Or, mountains, the singular number for the plural; these barbarous and monstrous persons either chose to live in the dens or caves, which were frequent in the mountains of those parts, or else they were driven thither by the arms and success of the Israelites. From Debir - From the territories belonging to these cities, as we have often seen in this history, cities mentioned for the country subject to them. The mountains of Israel - It doth not follow from hence, that this book was written by some other person long after Joshua's death, even after the division of the Israelites into two kingdoms. of Israel and Judah; but only that this was one of those clauses which were added by Ezra or some other prophet; though that be not necessary: for since it was evident to Joshua, from Gen 49:10, and c. that the tribe of Judah was to be the chief of all these tribes, and some dawnings of its eminency appeared in that time, in their having the first lot in the land of Canaan, chap.15:1, and the largest inheritance, chap.19:9, it is no wonder that it is mentioned apart, and distinguished from the rest of the tribes of Israel, though that also be one of them. But how could Joshua utterly destroy these, when Caleb and Othniel destroyed some of them after Joshua's death? chap.14:12 Judg 1:10 - 12. This might be, either Because these places being in part destroyed and neglected by the Israelites, were repossessed by the giants, and by them kept 'till Caleb destroyed them. Or rather Because this work, though done by the particular valour of Caleb, is ascribed to Joshua as the general of the army, according to the manner of all historians; and therefore it is here attributed to Joshua, though afterwards, that Caleb might not lose his deserved honour, the history is more particularly described, and Caleb owned as the great instrument of it, chap.14:6 - 15 and Judg 1:12 - 20.

Matthew Henry's Concise Commentary

11:15-23 Never let the sons of Anak be a terror to the Israel of God, for their day to fall will come. The land rested from war. It ended not in a peace with the Canaanites, that was forbidden, but in a peace from them. There is a rest, a rest from war, remaining for the people of God, into which they shall enter, when their warfare is accomplished. That which was now done, is compared with what had been said to Moses. God's word and his works, if viewed together, will be found mutually to set each other forth. If we make conscience of our duty, we need not question the performance of the promise. But the believer must never put off his armour, or expect lasting peace, till he closes his eyes in death; nay, as his strength and usefulness increase, he may expect more heavy trials; yet the Lord will not permit any enemies to assault the believer till he has prepared him for the battle. Christ Jesus ever lives to plead for his people, and their faith shall not fail, however Satan may be permitted to assault them. And however tedious, sharp, and difficult the believer's warfare, his patience in tribulation may be encouraged by the joyfulness of hope; for he will, ere long, rest from sin and from sorrow in the Canaan above.