Pillar three of the Responsibility to Protect (RtoP) focuses on the international community's responsibility to take 'timely and decisive action' to prevent and halt genocide, ethnic cleansing, war crimes, and crimes against humanity in those instances where a state is unable or unwilling to protection its own populations. A range of tools have been devised to aid in this 'timely and decisive action': economic sanctions, international criminal trials, and, most controversially, the use of force. The recent crises that have erupted in places such as Libya, Syria, and the Central African Republic highlight the continued relevance of the RtoP debate, but it also gives rise to the need to better understand the processes, opportunities and risks involved in moving from the RtoP as a norm to its operationalization under the third pillar. This book analyses the timeliness, legitimacy, proportionality, and effectiveness of pillar three responses through a series of chapters looking at international law, economic sanctions, military intervention, and alternative actions.