The geographical location of Briançon has been the subject of much attention and covetousness, especially from 1690 onwards after the alliance between France and the Duchy of Savoy ended. Its strategic role was then asserted, pushing for the permanent occupation of the threatening positions. Vauban and his successors reinforced, developed, and linked the fortifications of the city, which form a line of defense testifying to the evolution of the French military architecture.