Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 57. Ruses of War
According to the UK Military Manual (1958), “ruses of war are the measures taken to obtain advantage of the enemy by mystifying or misleading him. They are permissible provided they are free from any suspicion of treachery or perfidy and do not violate any express or tacit agreement.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 307.
The manual notes: “According to the debate which took place at the [Hague] Conference … [Article 24 of the 1907 Hague Regulations] must not be taken to imply that every ruse is permissible. A ruse ceases to be permissible if it contravenes any generally accepted rule.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 307, footnote 1.
According to the manual, “legitimate ruses” include:
Surprises; ambushes; feigning attacks, retreats or flights; simulating quiet and inactivity; giving large strong points to a small force; constructing works, bridges, etc., which it is not intended to use; transmitting bogus signal messages, and sending bogus despatches and newspapers with a view to their being intercepted by the enemy; making use of the enemy’s signals, watchwords, wireless code signs and tuning calls, and words of command; conducting a false military exercise on the wireless on a frequency easily interrupted while substantial troop movements are taking place on the ground; pretending to communicate with troops or reinforcements which do not exist; moving landmarks; constructing dummy airfields and aircraft; putting up dummy guns or dummy tanks; laying dummy mines; removing badges from uniforms; clothing the men of a single unit in the uniform of several different units so that prisoners and dead may give the idea of a large force; giving false ground signals to enable airborne personnel or supplies to be dropped in a hostile area, or to induce aircraft to land in a hostile area. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 312.
The manual also states: “A capitulation … may not … be annulled because one of the parties has been induced to agree to it by ruse.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 484.
The UK LOAC Pamphlet (1981) states: “Ruses of war … are permitted. They are acts intended to mislead an enemy but not inviting his confidence.” 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 4, p. 12, § 2(a).
According to the manual, ruses of war include the use of camouflage, decoys, mock operations, dummy installations, misleading messages and misinformation. 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 4, p. 12, § 2(a) and Annex A, p. 46, § 4.
The UK LOAC Manual (2004) states:
Ruses of war are not prohibited. Such ruses are acts which are intended to mislead an adversary or to induce him to act recklessly but which infringe no rule of international law applicable in armed conflict and which are not perfidious because they do not invite the confidence of the adversary with respect to protection under the law. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.17.
In its chapter on maritime warfare, the manual states:
Ruses of war are permitted. Warships and auxiliary vessels, however, are prohibited from launching an attack whilst flying a false flag, and at all times from actively simulating the status of those vessels exempt from attack. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 13.82.
With regard to internal armed conflict, the manual states: “Ruses of war are permitted.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 15.12.
As an example of a ruse of war, a commentator recalled that, during the War in the South Atlantic, the United Kingdom announced the establishment of a “maritime exclusion zone”. The impression was given that a UK nuclear submarine was on station in the area. There were later complaints that misleading information had been released, when it was discovered that the vessel was in Scotland. Since the exclusion zone was not a formal blockade (it only applied to enemy naval vessels), which must be enforceable to be binding, it could be considered as a mere warning to Argentine naval forces. The commentator stated that “this was a perfectly valid and successful piece of ‘disinformation’”. 
Howard S. Levie, “The Falklands Crisis and the Laws of War”, in Alberto R. Coll and Anthony C. Arend (eds.), The Falklands War: Lessons for Strategy, Diplomacy and International Law, George Allen & Unwin, Boston, 1985, p. 65.
A training video on IHL produced by the UK Ministry of Defence states that ruses are permitted but underlines that it is difficult to differentiate ruses of war and treachery. 
United Kingdom, Ministry of Defence, Training Video: The Geneva Conventions, 1986, Report on UK Practice, 1997, Chapter 2.4.