Sparta needed more land to farm for a booming population. So, logically, they took it. This caused the Helots(essentially slaves who were farming for them) to in turn revolt(after some time). Yet, this time the population issue was reversed, Helots out numbered the Spartans 10 to 1. To keep the Helots in check, Sparta started teaching strict discipline and military mindset to the boys in school. This was to teach obedience, and have them to join their ranks.
