Under international humanitarian law it is prohibited to make the object of attack a person who has surrendered. This article explores the circumstances in which the act of surrender is effective under international humanitarian law and examines, in particular, how surrender can be achieved in practical terms during land warfare in the context of international and non-international armed conflict. First, the article situates surrender within its broader historical and theoretical setting, tracing its legal development as a rule of conventional and customary international humanitarian law and arguing that its crystallisation as a law of war derives from the lack of military necessity to directly target persons who have placed themselves outside the theatre of armed conflict, and that such conduct is unacceptable from a humanitarian perspective. Second, after a careful examination of state practice, the article proposes a three-stage test for determining whether persons have surrendered under international humanitarian law: (1) Have persons attempting to surrender engaged in a positive act which clearly reveals that they no longer intend to participate in hostilities? (2) Is it reasonable in the circumstances prevailing at the time for the opposing force to discern the offer of surrender? and (3) Have surrendered persons unconditionally submitted to the authority of their captor?