Hope this wasn't answered anywhere else but I didn't find it at least. Now I know Roman troops radically change with a Marian trigger, but how many other countries will have a sort of evolution like that (assuming any had such a thing historically). Though I'm not sure about it historically, I would be surprised to find that Gauls of 250 BC were using the same sort of military as those in 50 BC. Though, I suppose improved barracks might partially be able to show this.