The county of Savoy transitioned, in the eleventh century, from a sub-division of the kingdom of Burgundy to a principality of the Holy Roman Empire. Governed by the homonymous dynasty—that of the Savoy—the county soon expanded to include territories on both sides of the Alps. During the principality of Peter II (1263–8), it evolved into a princely state endowed with an embryonic administrative system. Nicknamed “the gatekeepers of the Alps,” the Savoy rulers reached the plains; they had access to the Mediterranean Sea (Nice, 1388), and they controlled (Lausanne, Turin, Nice) or encircled (Geneva, Sion) the main cities of the western Alpine arc. After great conquests and military expeditions abroad during the fourteenth century, a period of expansion that gave the principality a certain territorial homogeneity and international renown, Savoy reached its maximum extension under the government of Amadeus VIII (1391–1440), the first Duke of Savoy. Known for his actions as a diplomat during the last phase of the Hundred Years’ War, Amadeus VIII reformed his armies, both tactically and administratively, by institutionalizing the office of the marshal (the head of the army) and that of the treasurer of wars. Despite his nickname “the Pacific,” which has been given to him by traditional historiography, his principate saw many large-scale military operations and coincided with the golden age of medieval Savoy. Afterwards, the principality of Savoy was in a profound institutional and financial crisis from the reign of Louis I (1440–65) until the reign of Emanuel Philibert (1553–80). During this period of growth that was followed by a period of decline, war played a fundamental role. The good condition of the sources available about this period, kept at the State Archives in Turin, has made it possible to reconstruct quite accurately several aspects of warfare, particularly the number of soldiers enlisted, and the material resources that were deployed, as well as the costs involved in the expansionist policy of the princes.