The Invisible War: Spies, Ambassadors and Espionage in the Old World

From the introduction: Even through the most peaceful eras of its existence the Empire has been waging a constant war unseen and unnoticed by the vast majority of its citizens – a war of espionage, intrigue and diplomacy. This invisible war has both a domestic and international dimension. Every country in the Old World has spies in the prominent courts and trading centres of the other nations.