alt Hacker NewsBack in the old days people were much more unabashed about such things. What's the purpose of your very small collection of city states? Obviously to expand, and smash any neighboring states. If you succeed, kill all the men and take their women as slaves. This was much of civilization for a long time.
Tja, IAMNAH, but my impression is that there is much more diversity to history than that. Not all groups attempted to expand, and among those who did there are many who swallowed up close by groups without violence (rather through 'cultural victory' so to say). It might even be the norm historically.