An armed humanitarian intervention must have a reasonable prospect of success to be justified. It must also be a proportional last resort. These are necessary conditions for legitimate AHI. It has been suggested that, in addition to these necessary conditions, there are also ideal conditions of AHI, namely disinterest and multilateralism. These conditions are said to enhance the moral credentials of an armed intervention without being strictly required. The paper concerns itself with the relationship between these two ideals and the (...) requirement of a reasonable prospect of success. Specifically, I explore the suggestion that the former are in some way instrumental to the latter. On this view, we should aspire towards disinterest and multilateralism because these things contribute to a positive humanitarian outcome. If this is correct then the ideal conditions can be partly grounded in, or justified in reference to, the prospect of success principle. (shrink)