so economically speaking it was cheaper to mass produce iron weapons.. I would have assumed a first mover advantage. It would be surprising if iron tech sprung up everywhere at the same time. And sure smaller groups could do it, but some groups would do it better,faster, cheaper (paretto principle). They should have had a material advantage me thinks. Since its cheaper you could arm more people perhaps. Lastly, the current powers could have also adopted iron and armed larger armies.