It's two hundred years from the war, it would be really hard to salvage steel with it being exposed fot this long.
They probably started with scavenging but moved to mining it. Even depleted mines usually contain enough material it's just can't be used due to small volume, but when your whole nation is 1-2 million people it will work.
They can make fabrics from whool, or nettle or any native local plant.
Why would you need to defend anything?