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United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 47. Attacks against Persons Hors de Combat
Section B. Specific categories of persons hors de combat
The UK Military Manual (1958) provides:
It is forbidden to kill or wound an enemy who, having laid down his arms, or having no longer the means of defence, has surrendered at discretion, i.e., unconditionally … A combatant is entitled to commit acts of violence up to the moment of his surrender without losing the benefits of quarter. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 119.
The manual also states: “Even if a capitulation is unconditional, the victor has nowadays no longer the power of life and death over his prisoners, and is not absolved from observing the laws of war towards them.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 476.
The UK LOAC Pamphlet (1981) provides that it is forbidden “to kill or wound someone who has surrendered, having laid down his arms, or who no longer has any means of defence”. 
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(b); see also Annex A, p. 44, § 12 and p. 47, § 10(f).
The Pamphlet also states: “Shipwrecked persons may not be made the object of attack.” 
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 7, p. 26, § 2.
The UK LOAC Manual (2004) states:
“A person who is recognized or who, in the circumstances, should be recognized to be hors de combat shall not be made the object of attack.” A person is hors de combat if:
a. “he is in the power of an adverse Party”;
b. “he clearly expresses an intention to surrender”; or
c.“he has been rendered unconscious or is otherwise incapacitated by wounds or sickness, and therefore is incapable of defending himself”;
“provided that in any of these cases he abstains from any hostile act and does not attempt to escape.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.6.
The manual further states:
The Hague Regulations 1907 are now recognized as part of customary law. Those regulations provide that the following acts are “especially forbidden”:
c. to kill or wound an enemy who, having laid down his arms, or having no longer means of defence, has surrendered at discretion. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 16.27.
Under the UK ICC Act (2001), it is a punishable offence to commit a war crime as defined in Article 8(2)(b)(vi) of the 1998 ICC Statute. 
United Kingdom, ICC Act, 2001, Sections 50(1) and 51(1) (England and Wales) and Section 58(1) (Northern Ireland).
The Eck case (The Peleus Trial) before the UK Military Court at Hamburg in 1945 concerned the sinking, during the Second World War, of a Greek steamship by a German U-boat on the high seas and the subsequent killing of shipwrecked members of the crew of the Greek boat. Four members of the crew of the German U-boat were accused of having violated the laws and usages of war by firing and throwing grenades on the survivors of the sunken ship. The Court held that there was no case of justifiable recourse to the plea of necessity when the accused killed by machine-gun fire survivors of a sunken ship, in order to destroy every trace of sinking and thus make the pursuit of the submarine improbable. In summing up, the Judge Advocate underlined that it was a fundamental usage of war that the killing of unarmed enemies was forbidden as a result of the experience of civilized nations through many centuries. He also stated that to fire so as to kill helpless survivors of a torpedoed ship was a grave breach of the law of nations. He added that the right to punish the perpetrators of such an act had clearly been recognized for many years. The accused were found guilty of the war crimes charged. 
United Kingdom, Military Court at Hamburg, Eck case (The Peleus Trial), Judgment, 20 October 1945.
In the Renoth case before the UK Military Court at Elten in 1946, the accused, two German policemen and two German customs officials, were accused of committing a war crime for their involvement in the killing of an Allied airman whose plane had crashed on German soil. After he had emerged from his aircraft unhurt, the pilot was arrested by Renoth, then attacked and beaten, before Renoth shot him. All the accused were found guilty. 
United Kingdom, Military Court at Elten, Renoth case, Judgment, 10 January 1946.
In the Von Ruchteschell case before the UK Military Court at Hamburg in 1947, the accused was charged, inter alia, of having continued to fire on a British merchant vessel after the latter had indicated surrender. He was found guilty on that count. The central question concerned the ways of indicating surrender. The Court noted that, even if the accused did not receive a signal of surrender, he could still be convicted because he “deliberately or recklessly avoided any question of surrender by making it impossible for the ship to make a signal”, which constituted a violation of the customary rules of sea warfare. 
United Kingdom, Military Court at Hamburg, Von Ruchteschell case, Judgment, 21 May 1947.
In 1982, in reply to a question in the House of Commons, the UK Prime Minister stated that, following the sinking of an Argentine cruiser by a UK warship during the war in the South Atlantic, another UK warship returning to the area where the sinking had occurred was instructed not to attack warships engaged in rescuing the survivors. 
United Kingdom, Letter of the Prime Minister in reply to a question asked in the House of Commons on the subject of the Falkland Islands situation, 1982, BYIL, Vol. 55, 1984, p. 595, § 13.
A training video on IHL produced by the UK Ministry of Defence illustrates the rule that “it is forbidden to kill or wound anyone who has laid down arms”. 
United Kingdom, Ministry of Defence, Training Video: The Geneva Conventions, 1986, Report on UK Practice, 1997, Chapter 2.1.
In 1991, before the UK Parliamentary Defence Committee, the officer commanding the UK forces in the Gulf War confirmed that the rules of engagement were modified in order to minimize casualties when it was realized that the Iraqis were seeking to surrender (the initial rules of engagement were to destroy the enemy). The plan was adjusted to encourage surrender rather than resistance. 
United Kingdom, Minutes of Evidence taken before the Parliamentary Defence Committee, 8 May 1991, Defence Committee’s Tenth Report, 1991, § 86.
In 2003, in reply to a written question in the House of Commons, the UK Secretary of State for Defence wrote:
The Coalition have dropped approximately 32 million–33 million leaflets aimed at Iraqi citizens, mainly combatants, but also civilians.
Those aimed at combatants include instructions on how to surrender, including adopting a non-offensive posture, raising a white flag, stowing weapons, and parking combat vehicles in a square formation.
In addition, the Coalition have used radio and loudspeaker broadcasts to convey specific surrender instructions to combatants. 
United Kingdom, House of Commons, Written answer by the Secretary of State for Defence, Hansard, 10 April 2003, Vol. 403, Written Answers, col. 351W.
In 2010, in its closing submissions to the public inquiry into the circumstances surrounding the death of Baha Mousa and the treatment of those detained with him by UK armed forces in Iraq in 2003, the UK Ministry of Defence stated:
12. The treaties setting out rules of IHL are supplemented by rules of customary international law (CIL), i.e. rules which are recognized as binding by States, even though they do not appear in treaty texts. … [I]n relation to the rules described below the Government accepts that they reflect CIL. It is suggested that the rules which are of most relevance to this inquiry are:
12.1. … A person hors de combat is: (a) anyone who is in the power of an adverse party; ... provided he or she abstains from any hostile act and does not attempt to escape.
12.2. … Thus, as persons in the power of UK forces the detainees all fell within the definition of persons hors de combat.  
United Kingdom, Ministry of Defence, Closing Submissions to the Baha Mousa Public Inquiry on Modules 1–3, 25 June 2010, §§ 12(1)–(2), p. 28.