Modern warfare has shifted from the traditional conception of states involved in self-defensive wars to include peacekeeping missions, humanitarian intervention, regional stabilisation in the face of natural disasters, and more. A central criterion from just war traditions is the probability of success—given the magnitude of harms that large military operations are expected to cause; there must be some likelihood that the military operation will be successful. However, how likely a given military operation will be is dependent, in part at least, on the capacities of those acting in the given military operation. Our paper shows that the capacities of those involved in a military action bear upon the likelihood of that operation being successful. A central goal of this paper is to argue for the recognition of the training of soldiers as a moral requirement for the just war.