And then we have the poetry of Tyrtaios, referenced in a previous post, who described the Spartans in battle. Remember he is contemporary to the Second Messenian War.
"For those who, remaining beside one another, dare to go into the hand-to-hand fight and the front rank, fewer die, and they preserve the people behind them. But of men who have begun to tremble every excellence is lost, and no one would ever finish speaking all the ills which happen to a man if he suffers something shameful. For attractive it is to split from behind the back of a fleeing man in hostile war, but shameful is a corpse lying in the dust with the head of a spear driven through its back.