It was Lycurgus who, in a time of great stress, convinced the Spartan people to adopt a new way of life – create a warrior class to protect Sparta from a revolt of the Messenian Helots. But it was a pact with the devil, because the subjugation of a people as slaves, requires the military might to hold down the inevitable revolts.
So the Agoge was adopted; twenty years military training for all young men starting when they reached age seven. Living together and fighting together – a lifelong bond between warriors.