At the beginning of the 18th century, Hungary and the Southern Netherlands are coveted by the French diplomacy. Those peripheral provinces of The Habsburg Empire oppose the centralization policy lead by Madrid and Vienna. In order to realize his dynastic ambitions, Louis XIV uses this context to destabilize these territories during the War of the Spanish Succession triggered by the death of the last Habsburg King of Spain, Charles II, the first November 1700. Louis XIV mobilizes his army and his ambassadors in the continuity of the foreign alliances « Alliance de revers » that have been conducted during centuries. The marquis des Alleurs and the president Pierre Rouillé de Marbeuf, agents of Louis XIV, half spy, half ambassadors, are respectively send in Hungary nearby the rebel prince François Rakoczi and in the Southern Netherlands nearby the general governor of the province and Elector of Bavaria, Maximilien-Emmanuel de Wittelsbach. Far from the din of the battlefield of the Spanish Succession, another war hardens. The battle for information’s became the first preoccupation of European courts. The confidentiality of the epistolary correspondences is a crucial object of attention. The purpose of this study is to define the framework of the French ambitions in Hungary and the Southern Netherlands at the beginning of the 18th century. The « alliance de revers » and military moves during the War of the Spanish Succession replace those two European countries at the heart of dynastic, diplomatic and military conflicts opposing the Bourbon’s and the Habsburg’s for European hegemony. ; Au début du XVIIIe siècle, la Hongrie et les Pays-Bas méridionaux sont l’objet de la convoitise de la diplomatie française. Ces provinces périphériques de l’Empire habsbourgeois s’opposent aux politiques de centralisation menées par Madrid et Vienne. Afin de réaliser ses ambitions dynastiques, Louis XIV utilise ce contexte pour déstabiliser ces territoires dans le cadre d’une guerre de Succession d’Espagne engendrée par le décès de ...