This Adelphi examines the difficulty the US armed forces face in shifting their focus from preparing for regular wars, in which combat is separated from civil society, to irregular wars, in which combat is integrated with civil society. It argues that the political context of contemporary irregular wars requires that the purpose and practice of Western forces be governed by liberal values. This is also the case with regular wars, to the extent that they occur, but it is the integration with civil society that makes the application of liberal values so challenging. It argues that this challenge becomes easier to meet when military operations are understood to contribute to the development of a compelling narrative about the likely course and consequence of a conflict, in which these values are shown to be respected. However, while it is vital that the employment of armed force remains sensitive at all times to the underlying political context and to the role of narratives in shaping this context, a key test of success will always be the defeat of the opposing forces. The application of this test in regular war remains straightforward; this is not the case with irregular war, which can be of long duration and contain frequent shifts in tempo and focus. The ‘war on terror’ has highlighted these issues and the paper concludes with suggestions for a strategic response.