Tensions between civil and military authorities over issues such as budgets and strategic posture are unavoidable in pluralistic societies. Scholars of Civil-Military Relations (CMR) have identified a range of practices through which civil-military contestation occurs, and examined their implications for issues such as military effectiveness. This literature, however, has yet to incorporate critical approaches to knowledge into its analysis. Seeking to fill this gap, this article explores how the British military's presentation of its professional knowledge has been increasingly shaped by the political context of British defence policy. More specifically, it argues that the British armed forces' presentation of opaque imaginations of future war in military doctrine has sought to entrench the role of Defence in an environment of increasingly integrated governmental responses to security challenges. To do this, the article focuses specifically on two concepts that have become increasingly significant in the British defence establishment's articulation of its professional authority and strategic purpose - Multi-Domain Integration (MDI) and the Integrated Operating Concept (IOpC). The article therefore contributes to the literature a fresh perspective of the role of military doctrine and epistemic practices in civil-military contestation, as well as a critical account of the politics of knowledge in British defence.