This chapter defends the Duty View of punishment. According to this view, the permissibility of punishing offenders for reasons of general deterrence are grounded in the enforceable duties that offenders incur as a result of their wrongdoing. This view is defended by examining the relationship between self-defence, compensatory harm, and punishment. The chapter aims to demonstrate that the main differences between self-defence and punishment do not provide morally compelling reasons against punishing offenders on defensive grounds. Harming offenders as a means to avert threats posed by others can be justified in virtue of the duties that offenders owe to their victims - duties that they incur by wronging their victims.