But it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and carries his banner openly.
But the traitor moves amongst those within the gate freely, his sly whispers rustling
For the traitor appears not a traitor; he speaks in accents familiar to his victims, and he wears their face and their arguments, he appeals to the baseness that lies deep in the hearts of all men.
A murderer is less to be feared."
-- Marcus Tullius Cicero