So Joshua took all that land, the hill-country, and all the South, and all the land of Goshen, and the lowland, and the Arabah, and the hill-country of Israel, and the lowland of the same;
This paragraph makes pointed mission of God's hardening the hearts of the Canaanites in order to assure their destruction by Israel  (Joshua 11:20).  God's judicial hardening of unrepentant sinners is a phenomenon conspicuously evident in both the O.T. and the N.T.  God's hardening the hearts of evil men does not exonerate or excuse their wickedness and rebellion.  It just means that when a human being has morally rejected God's claim upon his life and persists in a course of wickedness, that God retaliates against that person by "hardening" or "darkening" his heart, thus enabling the wicked one to walk in the way he has chosen without further restraint.  Paul mentioned this in Romans, and it appears that a course of wickedness willingly pursued by a sinner will result, even in these present times, in God's disabling, darkening, or hardening his mind (the Biblical "heart"), so that, having already chosen evil, the hardened soul is incapable of intelligent decisions involving morality, and even including many practical considerations.  Even a fool, for instance, should have known better than to rush into the Red Sea following Israel's crossing, but Pharaoh, whose heart the Lord had hardened, went right in with his whole army, only to be drowned!  Just so, here it seems that the "intelligent" Jabin should already have caught on from the instances of Jericho and Beth-horon that God Himself was helping Israel.  Therefore, when this "intelligent" sinner formed his coalition against Israel, he merely proved what a fool he was!  Just so, today, there are men with high positions of academic, political, or social power who are BLIND indeed to the simple truth of Christianity.  Why?  They love evil; they have already elected evil as their preferred course.  And God has hardened their hearts! (See  2 Thessalonians 2:10-12.)