Who where the spartans?

Who where the Spartans warriors? Spartans where some of the most feared warriors in the old world of Greeks and romans some say they alone stood up against 3 million Persian soldiers said to be armed solely with iron armor and weapons the Spartans trained since they where7 and started fighting wars when they where 18 they weren't very many of them but if the Greek nations where fighting you wanted Spartans on your side they where the best soldiers in the Greece