I dunno. Spies - and indeed many other features in TW - are an abstract. No-one is surely suggesting that one man can act in this manner as a spy, and that he would be so hugely expensive to recruit and maintain. Ancient societies of all types used bribery, subterfuge and espionage type activities. Agents might not be recruited and employed directly by states, but would have provided detailed and relevant information to however was paying them at that time. The fact that "spies", "diplomats" and "assassins" are used in game to represent a complex system of information gathering and behind the scenes activities is just that a representation. If anything there should be more of this kind of activity in the game.

One thing that features in a massive number of ancient military campaigns for example is that they would be advised by a rival to the throne of the place they were attacking.