19. the Lord was with Judah; . . . but they could not drive out the inhabitants of the valley--The war was of the Lord, whose omnipotent aid would have ensured their success in every encounter, whether on the mountains or the plains, with foot soldiers or cavalry. It was distrust, the want of a simple and firm reliance on the promise of God, that made them afraid of the iron chariots (see on Jos 11:4-9).

JFB.