Philosophers working on the morality of harm have paid surprisingly little attention to the problem of manipulation. The aim of this paper is to remedy this lacuna by exploring how liability to defensive harm is affected by the fact that someone posing an unjust threat has been manipulated into doing so. In addressing this problem, the challenge is to answer the following question: Why should it be the case that being misled into posing an unjust threat by manipulation makes a (...) difference to one’s liability, as compared to being misled into doing so by natural events or by someone’s honest attempt to persuade us? To answer this question, I first outline an account of manipulation and then use it to defend what I shall call the “Pre-emption Principle.”. (shrink)