A king of France might send letters on the same day to the count of Flanders, who was definitely his vassal but a very independent and unruly
one, to the count of Luxemburg, who was a prince of the Empire but who held a money-fief (a regular, annual pension) of the king of France, and to the king of Sicily, who was certainly ruler of a sovereign state but was also a prince of the French royal house. In such a situation one could hardly distinguish between internal and external affairs. (p. 83)
