 The “reasonable prospects of success” criterion is a surmountable hurdle on the way to proportionality. Typically, if a war lacks reasonable prospects of success, then it will be disproportionate, since wars always involve causing significant harms, and if those harms are likely to be pointless then they are unlikely to be justified. But of course sometimes one’s likelihood of victory is very low, and yet fighting is still the best available option, and so necessary and proportionate. Having reasonable prospects of success matters only for the same reasons that necessity and proportionality matter. If necessity and proportionality are satisfied, then the reasonable prospects of success standard is irrelevant.