Chapter 4 is concerned with the classification of persons under the law of war. The Manual’s treatment of armed forces and the civilian population is discussed, and improvements to the Manual’s chosen language are proposed. The US position on unlawful combatants and unprivileged belligerents, as set forth in the Manual, is subjected to detailed critical analysis. In succeeding sections, the rights, duties and liabilities of combatants, the concepts of armed forces of a state, of militia and volunteer corps and of levee en masse as treated in the Manual are considered. Thereafter the Manual’s discussion, inter alia, of the rights, duties and liabilities of civilians, the status, rights and responsibilities of military medical and religious personnel, of auxiliary medical personnel and of personnel engaged in the protection of cultural property is evaluated. After addressing the complexities associated with persons authorised to accompany the armed forces, the Chapter reviews the Manual’s treatment of crews of the merchant marine and of civil aircraft, spies, saboteurs, private persons who engage in hostilities and the rights, duties and liabilities of unprivileged belligerents, of mercenaries and of a number of other classes of person who are the subject of specific law of war provision.