In Plato's Republic, Socrates proposes a class of "Guardians" whose duty is to protect and rule over the ideal city. Guardians are selected in early childhood, at which time they begin receiving education. Like the very best guard dogs, Guardians must be "gentle with friends and savage with enemies," among other qualities. Socrates conceived of the Guardians as individuals of high intelligence and sophistication, not mere warriors, meaning that, as far as most of Plato's past and present students are concerned, Achilles would have probably failed to make the grade as one of Socrates' Guardians, his CV as a consummate warrior notwithstanding. In contrast, the Trojan hero Hector -- defender of his city and its people -- probably would have. In this column on security, Mike Parks explains why learning from ancient warriors and warrior cultures is essential to maintaining an edge, even in modern society. ...