From Introduction: The Spy of the High Middle Ages and Renaissance is not the equivalent of the modern spy or secret agent employed by the nation-state. The Spy is as likely to be a merchant who trades regularly with a foreign country as a professional hunter of secrets. Spy networks of the Middle Ages and Renaissance were no less complex than in modern times, but due to the difficulties of communications over long distances, and the lack of aerial or satellite reconnaissance, the secrets which the Spy seeks may be as mundane as how many troops in a particular army. In modern times, this knowledge is accessible to the general public through certain periodicals or information archives. In the past, often a king did not know the precise numbers of his army.