In the summer of 2015, the French section of Médecins Sans Frontières started aid projects for migrant populations in Greece and France. The launch of these operations was the occasion for lively discussions within the association, both in terms of public positioning (how to justify an intervention in a rich country and not get lost in "political" territory?), and in terms of revising our operating methods, knowing that the primary needs of migrants were not primarily medical. Some people then recalled the association's militant practices in the 1990s, which were sometimes considered as abuses. By retracing the history of the French Mission, Michaël Neuman seeks to understand, with regard to the migration issue, the complex articulation between operational constraints, political positioning and militant practices.