How do militaries push back when they oppose civilian initiatives? This article analyses the sources and character of military dissent, focusing on the United States. It details the sources of military preferences over policy and strategy outcomes, emphasising the interplay of role conceptions with other material and ideational factors. It then presents a repertoire of means – tactics of dissent – through which military leaders can exert pressure, constraining and shaping civilians’ decision-making calculus and the implementation of policy and strategy choices. Empirically, it traces military dissent in the 1990s-era humanitarian interventions; the US's ‘War on Drugs’ beginning in the 1980s; and the Afghanistan surge debate in 2009. In so doing, the article contributes to a broader research programme on military dissent across regime types. It also expands scholars’ understandings of preference formation within militaries and illuminates the various pathways through which military dissent operates and potentially undermines civilian control.