It needed to match the Sturmgewehr’s light weight and fast, automatic fire. It needed to be cheap and simple to manufacture. And perhaps above all, it needed to be capable of functioning reliably in the incredibly difficult and diverse conditions of Russian warfare; you had to be able to shoot, strip and clean it with gloves on. It needed to work wet, dry, full of mud or sand. It needed to operate with wide enough tolerances such that its metal could expand and contract between the icy Russian winter and the warm summer, and the gun would still operate. Kalashnikov made his first sketches right there in his hospital bed.