Adam Clarke on Joshua 14:12

I shall be able to drive them out - He cannot mean Hebron merely, for that had been taken before by Joshua; but in the request of Caleb doubtless all the circumjacent country was comprised, in many parts of which the Anakim were still in considerable force. It has been conjectured that Hebron itself had again fallen under the power of its former possessors, who, taking the advantage of the absence of the Israelitish army, who were employed in other parts of the country, re-entered the city, and restored their ancient domination. But the first opinion seems best founded.