Doctrines are considered a key component of military power, shaping the ways in which armed forces organize and operate. This study critically examines the assumption that armed forces can change their practices by writing formal doctrine. The study addresses the research problem of why some formal doctrines are implemented and others are rejected. It does so by developing and testing a novel theoretical framework on doctrinal implementation through a comparative case study on rejection of the US Army 1976 Active Defense doctrine and successful implementation of the 1982 AirLand Battle doctrine. The study shows that contrary to popular beliefs, the actual concepts within a formal doctrine do not seem crucial for whether it is implemented or rejected. Rather, cultural coherence and inclusive creation seem crucial in this regard.