Scholars often argue that the culture of American constitutionalism provides an important constraint on aggressive national security practices. This Article challenges the conventional account by highlighting instead how modern constitutional reverence emerged in tandem with the national security state, critically functioning to reinforce and legitimize government power rather than primarily to place limits on it. This unacknowledged security origin of today’s constitutional climate speaks to a profound ambiguity in the type of public culture ultimately promoted by the Constitution. Scholars are clearly right to note that constitutional loyalty has created political space for arguments more respectful of civil rights and civil liberties, ma...