The Spartans are famous for many things, and their society was unique among the Greek city-states for a number of reasons. As the entire reason it could maintain such a formidable army, it relied heavily on a force of hereditary slaves, known as helots. But the foundation for it all came in the First Messenian War, which up until then Sparta had been just another Greek city-state, albeit with some unique laws and a professional army, while significant elements of it are probably mythologized, it is likely something approximating this happened. What if it resulted in a Messenian victory? Could we see a reverse Sparta, with the Spartiates becoming helots? Would we see straight up conquest/extermination? Or could a "league" of some sorts form? How would it impact the Archaic and Classical eras? How are the political systems and development of Hellas affected? Is the response to the Achaemenid invasion different from OTL, if it is not butterflied away? What is the influence outside Hellas?