what event in spartan history caused them to develop a strong military

The whole reason Sparta became that legendary military powerhouse really boils down to the Messenian Wars. See, the Spartans basically conquered their neighbors, the Messenians, and turned them into helots, which were essentially state-owned serfs. The problem for the Spartans was that there were way more helots than actual citizens, so they lived in constant, paralyzing fear of a massive slave revolt. It got to the point where they realized that if they didn't turn their entire society into a permanent army, they’d eventually lose everything to an uprising.

That fear is what triggered the radical reforms attributed to Lycurgus. They needed total control, so they shifted the entire culture toward the agoge, that brutal training system for boys. It wasn't just about being good fighters; it was about keeping the population in line and maintaining that rigid social structure. It’s honestly fascinating when you look at it, because their military obsession wasn't just about expanding territory, it was a survival strategy to keep their own labor force from tearing them apart. They basically sacrificed normal family life just to stay in power.