So I was going to ask a question regarding why the Central Asian peoples such as the Mongols and the Turks were able to so effectively invade the West, however I noticed that that question had already been asked and answered. As I understand it it was because they were able to mobilise literally their entire population of healthy adult males to fight, whereas settled cultures had maybe a few percent of their adult males able to fight.

However this leaves open the question: where did all the steel necessary to equip an army of hundreds of thousands of men (and their horses) come from? Surely that would require a significant mining operation, which would in itself require a settled, agrarian society to support the miners. Just how nomadic were the Central Asian peoples?