The recent resignation of Defense Secretary James Mattis reminds us that serving the nation at the strategic level is not an amoral activity, nor a place where realism pushes ethics off the stage or where Machiavelli is more useful than Aristotle. A lot has been written on the meaning of Secretary Mattis's resignation pointing out, correctly, that his was a principled resignation. But few say exactly what those principles are.

For me, a close reading of his resignation letter and understanding his reasoning can reveal how closely related are the strategic and the moral.