This article argues that the Responsibility to Protect (RtoP) adds value to international efforts to protect populations from genocide and mass atrocities, but not in the ways commonly thought. It suggests that RtoP is not particularly effective as a 'rallying call' that mobilises action in cases where international society may be initially reluctant to act. Where it does add value is in helping to reshape states' identities and interests such that consideration of the protection needs of populations, in relation to the threat of genocide and mass atrocities, has been internalised to some extent by the UN Security Council. As such, RtoP is best seen as being a 'habit former'. The principle does not, however, determine particular behaviours or guarantee international consensus because decision-making is heavily influenced by contextual factors. The argument proceeds in three parts. The first examines instances where RtoP has been invoked since early 2006. The second explores the role of context in shaping how the UN Security Council responds to particular crises. Finally, to amplify the points made in these sections, the third section considers the UN Security Council's response to the crisis in Somalia after 2006.