How do military ideas, and military doctrines in particular, spread through the international system? This article extends extant work on military diffusion by exploring why some states, after deciding to adopt another's innovative warfighting system, fail to implement it. The author argues that for states to successfully implement a military doctrine developed abroad, much information about the unobservable aspects of the warfighting system is needed. States vary in their capacity to acquire the necessary knowledge because they face differing levels of resistance to military diffusion within their armed forces. Powerful groups within the military that are opposed to such adoptions are likely to use their influence to press for policies and bureaucratic maneuvers that constrain information flows between innovating states and their own state and consequently inhibit implementation and diffusion of military doctrines. Therefore successful implementation of foreign military doctrines can be expected when states face minimal resistance within their militaries, and moderated or failed implementation can be expected when opposition is more significant. A provisional test of the argument is conducted through an assessment of Argentina, Brazil, and Chile's attempts to implement the German military doctrine at the turn of the twentieth century.