This article argues that the reduction of the morality of killing in war to the morality of killing in self-defense by ‘reductive-individualist’ revisionist just war theories is inconsistent, because when those theories apply the moral notion of self-defense to the morality of killing in war, they do not preserve the two conceptions of the “individual” inherent in this notion. The article demonstrates this inconsistency in two steps: First, it disentangles the two conceptions of the individual inherent to the notion of self-defense, namely (1) that the individual is an “entity” potentially bearing a right to self-defense (unlike, e.g., groups) and (2) that the individual is a “particular,” where “particular” signifies that every human is different from every other human. The conception of the individual as a “particular” is tied to the idea that a justification grounded in a rule of self-defense is necessarily “concrete,” in the sense of referring to individually given and specific perceptions or cases, as opposed to “abstract,” in the sense of being detached from specific perceptions or cases. The article then demonstrates that reductive individualism reflects the first notion of the individual, but not the second. Due to the “loss” of the individual as a “particular”, the reductive-individualist reduction of the morality of killing in war to the morality of killing in self-defense is inconsistent, and hence its justification of killing in war grounded in self-defense is not concrete. Since such a justification must be concrete, reductive individualism cannot offer a justification for belligerent killing.