Is there is a moral obligation to militarily intervene in another state to stop a genocide from happening (if this can be done with proportionate force)? My answer is that under exceptional circumstances a state or even a non-state actor might have a duty to stop a genocide (for example if these actors have promised to do so), but under most circumstances there is no such obligation. To wit, “humanity,” states, collectives, and individuals do not have an obligation to make (...) such promises in the first place or to create institutions that would impose a legal obligation of intervention upon them. Nor do states or persons or humanity “collectively” have – originally, without specifically creating such duties by contracts or promises – any pro tanto or special duties to save strangers at considerable cost to themselves or their own citizens (including their soldiers). That is, these costs do not merely override a duty to intervene, but rather there is no such duty to begin with – as shown by the fact that in such cases of non-intervention agents would not owe those they let die any compensation: if I do not save someone’s life because saving him would have cost me my arm or would have come with a high risk of losing my own life or would have forced me to kill innocent bystanders, I do not owe this person compensation. Thus the point of this chapter is that there is no “natural” or “general” or “original” duty to militarily intervene (or to create a legal obligation) to stop a genocide. I will consider and refute a number of arguments to the contrary, for example by Lango, Tan, and Pattison. (shrink)