Over the last decade, interest has grown in what is known as ‘humanitarian intervention’, that is to say, military intervention in another state, with or without the approval of that state, for humanitarian purposes, to prevent genocide or large-scale violations of human rights. A great deal has been written about whether such interventions are justified but much less about how such interventions should be carried out. It is often assumed that the use of military force is justifiable if the goals are worthwhile (jus ad bellum). Military force is often treated as if it were neutral, a ‘black box’ to be employed when other methods of achieving a particular political goal fail. However, the methods adopted must also be appropriate and, indeed, may affect the ability to achieve the goal specified. In other words, the ‘how’ is as important as the ‘why’. A humanitarian intervention has to be humane in means as well as goals, and that has far-reaching consequences for the conduct of military operations.