The orthodox account of the morality of war holds that the responsibility for resorting to war rests on the state's political authorities and the responsibility for how the war is waged rests only on the state's army and, thus, business firms have no special obligations in wartime. The purpose of this article is to reconsider the ethical responsibilities of business firms in wartime. I defend the claim that a plausible standard of liability in war must integrate the degree of the agent's contributions to posing an unjust threat, the nature of agent's behavior, and his/her intentions. If these premises are correct, it follows that the moral obligations of civilians and business corporations are fundamentally altered by war. Taking into consideration their relative contributions to the war effort, a taxonomy of business firms is developed.