The article analyses the role of secrecy in the development and production of military technology from the 18^th to the beginning of the 20^th century. Archival materials (the texts of secrecy oaths) from the chief arms manufactory in Tula allow a reconstruction of the old secrecy procedures and rules. The authors discuss how those procedures influenced the international exchange of military technical information in the development and manufacturing of small arms during the second half of the 19^th century. As a rale, under the existing economic conditions, secrecy went against the interests of the inventors. Material from German, Russian, and French sources shows how those restrictions were circumvented in reality. Neither secrecy, nor even military conflicts, could provide an ultimate barrier to exchanges in military technology, but they affected the intensity of such contacts and the boundary between legal and illegal forms of information exchanges. The historical dynamics of innovation allows further discussion of the relative disadvantages and advantages of secrecy in military research.