Sparta

Sparta conquered its neighbors and turned them into helots — a subject farming population outnumbering Spartans several times over. To hold them, Sparta remade itself into a permanent barracks: boys taken from home at seven, trained to fight for decades, citizens forbidden trade or craft because farming the helots' labor freed them for nothing but war. It produced the finest infantry in Greece and almost nothing else — no philosophy, little art, few buildings. Sparta is the clearest ancient case of a society organized entirely around holding down the people beneath it, and being shaped by the effort.