In 1865, Ambroise Baudry, the architect in charge of the Paris Opera House, and Gustave Boissière, a graduate of the Ecole Normale Supérieure specialising in Algerian archaeology, were sent on an archaeological mission to Iglitza in Romania by order of Napoleon III, in order to excavate the archaeological site of Troesmis. Located in Dobroudja, a region still under Ottoman domination, their mission in the Romanian Principalities showed a double interest, both scientific and diplomatic. Their aim was to search for traces of the Roman occupation on the territory and, in addition, Boissière was asked to evaluate the state of education in the principalities. During the second half of the 19th century, this coastal region of the Black Sea, little known archaeologically by Western specialists, was subject to practices and procedures similar to all regions under Ottoman rule (excavation permits, firman, etc.). The context in which the mission was carried out was therefore far from easy, which prompts us to reflect on the beginnings of classical archaeology and the growing interest in the practice of excavations in territories newly integrated into the French cultural sphere. This presentation aims to question the nature and context of this archaeological excavation. After an initial approach to the origin and development of the archaeological mission to Troesmis, we will then examine its diplomatic nature and finally address the reception of the mission. Our investigation will be based on the examination of archives, historical and archaeological studies in order to provide an analysis of Napoleon III's scientific mission and to understand the development of archaeology and its expansion outside Greece and Italy.