This article addresses a gap in the literature on military adaptation by focusing on the first step in the adaptive process: detecting failure. We argue that institutionalised feedback loops are a critical mechanism for facilitating detection. Feedback loops are most effective when they filter information and distribute lessons learned to senior tactical commanders. In turn, effective filtration depends on incorporating frontline soldiers and specialists into intelligence cells while creating a protected space for dissent. We evaluate our theory against both irregular and conventional wars fought by the British Army: the counterinsurgency campaign in the Southern Cameroons (1960–1) as well as the evolution of British assault tactics on the Western Front of the First World War (1914–18).