I received the following question:

In Judges 1:19, why can’t Judah drive out the inhabitants of the lowland because they had ¨chariots of iron¨?

Judges 1:19. So the LORD was with Judah. And they drove out the mountaineers, but they could not drive out the inhabitants of the lowland, because they had chariots of iron.

Judah was one of the most faithful tribes in the wars in the days after Joshua, working harder than many of the tribes to drive out the nations they were tasked with driving out and destroying. Yet as you point out, in this case they tried to drive these people out, but could not because of their chariots of iron. It is strange that the LORD would not give them the victory in this. Yet it could be that they were relying on their own strength, and not trusting in the LORD to give them this victory, as they should have been. Notice too Judges 3:1-2.

1. Now these are the nations which the LORD left, that He might test Israel by them, that is, all who had not known any of the wars in Canaan 2. (this was only so that the generations of the children of Israel might be taught to know war, at least those who had not formerly known it),

So it seems that the LORD had left a few nations not driven out in order to test later generations of Israelites to see if they would trust in Him in times of warfare. Clearly, they failed this test, and did not trust in Him. My point, though, is that these ones with the chariots of iron that Judah could not drive out may have been some of these that the LORD was not driving out in order to test later generations.

Other than this, it is hard to say. Ultimately, they would have driven them all out if they trusted in the LORD to do it. They left the task undone, however, and ultimately it was David who had to complete the accomplishment of it.