Judges 3:1-2--
1And these [are] the nations which Jehovah left, to try Israel by them, all who have not known all the wars of Canaan
2(only for the sake of the generations of the sons of Israel's knowing, to teach them war, only those who formerly have not known them) --
I am not sure if any of these nations are the same who had the iron chariots of chapter one, but it does remind us that God uses things---even evil things---for His purposes. ALL things are of God, as Paul wrote in 2 Cor. 5:18.
Astrapho, atheists can take hundreds and thousands of examples, both from the Bible and the world today, to argue that there is no God. Why? Because their minds are weak and carnal, and cannot grasp the sovereignty of God. They think that if there is a god, he (or it) would make all things perfect (from man's perspective), because that is what they want. And since all things aren't perfect right now, there must be no god.
This chariots of iron verse seems odd and hard to explain, but no more so than things you might see every day.
You see a crippled girl in a wheelchair who will never walk. That seems unfair. The atheist asks: If there's a God, why doesn't He make her walk?
You drive by a car accident. That seems unfair. The atheist asks: If God exists, why didn't He just prevent the crash?
These things are sad to us as well, even though we are believers, but we have the great comfort of knowing that God is working ALL things after the counsel of His own will (Eph. 1:11).