this paper advances a novel account of part of what justifies killing in war, grounded in the duties we owe to our loved ones to protect them from the severe harms with which war threatens them. It discusses the foundations of associative duties, then identifies the sorts of relationships, and the specific duties that they ground, which can be relevant to the ethics of war. It explains how those associa- tive duties can justify killing in theory—in particular how they can (...) justify overrid- ing the rights to life of some of those who must be killed to win a war. It then shows how these duties can be operationalised in practice: first, showing how soldiers who fight on behalf of their community can act on reasons that apply to the members of that community; second, showing that the argument from associative duties does not prove too much—in particular, that it does not license the intentional killing of noncombatants in war. (shrink)