The article looks at the origins and evolution of R2P and examines ongoing debates about it and the principle’s current status. Interventions were frequent before R2P was formulated in 2001 and are not guaranteed after R2P’s unanimous adoption in 2005. Atrocities will still be committed and the international community will struggle to respond to them in time and effectively. In contrast to controversial “humanitarian interventions”, R2P, especially when backed by legitimacy criteria that have been agreed in advance, at least helps to shift the balance towards interventions that are rule-based, multilateral and consensual. To that extent it helps the world to be better prepared – normatively, organizationally and operationally – to deal with crises of humanitarian atrocities, as they arise, without guaranteeing good outcomes.