This first, introductory chapter explains that the purpose of the book is to detail how international humanitarian law addresses development of autonomous weapon systems. IHL seeks to maintain a balance between competing concerns: primarily, the necessity for States to protect their national interests through military means when peace fails and their obligation to serve broader humanitarian goals by limiting the harm inflicted on those involved in armed conflict. Accordingly, the law must be revised and updated as the technology of war changes. The book discusses the ways in which law must respond to use of autonomous weapon systems in order to maintain the balance. The remainder of the chapter sets the scope of the discussion: the book does not advocate for or against autonomous weapons, only assesses their compatibility with existing IHL; it does not focus on any specific weapon system, but on autonomy as a capability; and the legal frame of reference is the First Additional Protocol to the 1949 Geneva Conventions.