I think there is a problem with knowledge being very dencly concentrated and supply chains being so long. If you took someone who worked in a steel mill I bet

I think there is a problem with knowledge being very dencly concentrated and supply chains being so long. If you took someone who worked in a steel mill I bet they would have no idea how to produce steel from first principles. They know what their job entails, they know which bits of equipment need serviced an maintained but they don't know how to get from rocks to bar stock. Similarly if you had a perfectly working steel mill and you cut the supply of coke or iron ore few would know how to get it up and running again. If you cut the supply of the alloying elements you might get a passable mild steel but not one to the exact specifications you require. I think it's probably surprising how few vital links you have to cut before life as we know it breaks down.