Can interventions be used to assist oppressed peoples in overthrowing their governments? According to the influential non-interventionist arguments of J.S. Mill and Michael Walzer, reform interventions are incompatible with a principle of national self-determination. This article challenges Mill and Walzer, arguing that, in limited cases, interventions could in principle support revolutionary movements in such a way as to facilitate democratic transition. It does so by tracing a lack of conceptual clarity back to Mill's argument in 'A Few Words on Non-Intervention'. In particular, it is argued that Mill's and consequently Walzer's account of domestic revolutionary conflicts fails to distinguish the salience of military from properly political forces. Mill's Considerations on Representative Government provides the starting point for a clearer set of distinctions through which to reconstruct the principle of non-intervention on a stronger footing.