Joshua made war a long time with all those kings.
18. Joshua made war a long time, etc Before, he had, in a short time, and, as it were, with the swiftness of running, seized possession of five kingdoms; in the others the case was different, not from hesitation, or weariness, or sloth, but because the Lord exercised his people variously, that he might give a brighter display of his manifold grace, which usually loses...
The Canaanites' refusal to seek peace was their fatal blindness. God hardened hearts already bent on war; they chose enmity with Israel when they might have made terms, as Gibeon did. Hardness of heart is the sinner's ruin, and those left to their own stubborn pride are already marked for destruction.
AI summary
Commenting on Joshua 11:15-23
Joshua made war a long time with all those kings. For, though the account of the conquest of them is put together, and lies in a small compass, yet those victories were not obtained at once, or in a few days, as were those of the five kings, and others, related in the preceding chapter, Jos 10:10; but were the work of some years; Josephus...