An auction for the barracks? The problem of troops lodging at the beginning of the French Third Republic - In France, the defeat of 1871 and the Commune accelerated the awareness of the social usefulness of the compulsory military service, theoretically universal but in fact thoroughly based on the obligation, on the part of the working classes, to pay the blood tax. Moreover, the politicians did not want to impose the cost of an increasingly bigger army entirely on the budget of the State. The two principles upon which the military reform of the 1870s was based the stay of the structures and the concentration of the units allowed the Minister of War to set up negotiations with the cities that were willing to host the new garrisons, in order to obtain local contributions to the construction of the necessary barracks. This article focuses on various aspects of such negotiations; on the one hand, in a historical moment in which the army is still seen as a potential threat to the republican order, the military managers strictly respect the parliamentary prerogatives and the regular procedures of the negotiations, in agreement with the Ministers of the Interior and of Finance. They are eager to end the instability of the government, which manifests itself in the composition of the town councils with which they carry on the negotiations. On the other hand, the latter face the problem carefully weighing the pros and cons of the money to spend in order to host the garrisons, paying more attention to the interests of business than to the patriotic duties of defense.