Revisionist approaches to the ethics of war seem to imply that civilians on the unjust side of a conflict can be legitimate targets of defensive attack. In response, some authors have argued that although civilians do often causally contribute to unjustified global threats – by voting for war, writing propaganda articles, or manufacturing munitions, for example – their contributions are usually too ‘small’, or ‘remote’, to make them liable to be intentionally killed to avert the threat. What defenders of this view lack, however, is a theory of causal contribution. This article sketches and defends a theory of causal contribution. We then apply it to the kinds of situation that defenders of the view are interested in. We argue, however, that...