Related Rule
Practice Relating to Rule 57. Ruses of War
Belgium’s Law of War Manual (1983) states: “Ruses of war are acts which, without constituting a violation of a recognized rule, are intended to mislead an adversary or to induce him to act recklessly.” It gives examples of ruses of war, such as surprise attacks, ambushes, feigning attacks, simulating quiet or inactivity, creating an impression of a stronger force than actually exists, making use of the enemy’s code, transmitting false messages and using an informal cease-fire intended to collect the wounded to execute unobserved movements. 
Belgium, Droit Pénal et Disciplinaire Militaire et Droit de la Guerre, Deuxième Partie, Droit de la Guerre, Ecole Royale Militaire, par J. Maes, Chargé de cours, Avocat-général près la Cour Militaire, D/1983/1187/029, 1983, p. 32.
Belgium’s Teaching Manual (1994) for Officers provides that ruses of war are authorized. 
Belgium, Droit de la Guerre, Manuel d’Instruction pour Officiers, Etat-Major Général, Division Opérations, 1994, Part I, Title II, p. 33.