Related Rule
United States of America
Practice Relating to Rule 47. Attacks against Persons Hors de Combat
Section B. Specific categories of persons hors de combat
The US Field Manual (1956) provides: “It is especially forbidden … to kill or wound an enemy who, having laid down his arms, or having no longer means of defense, has surrendered at discretion.” 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 29.
The US Air Force Pamphlet (1976) provides: “The law of armed conflict clearly forbids the killing or wounding of an enemy who, in good faith, surrenders.” 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 4-2(d).
Furthermore, the Pamphlet states: “In addition to the grave breaches of the Geneva Conventions of 1949, the following acts are representative of situations involving individual criminal responsibility: … deliberate attack on … shipwrecked survivors”. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 15-3(c)(1).
The US Soldier’s Manual (1984) forbids attacks against non-combatants, including soldiers who surrender or who are sick, wounded or captured. 
United States, Your Conduct in Combat under the Law of War, Publication No. FM 27-2, Headquarters Department of the Army, Washington, November 1984, p. 5.
The manual further states:
Enemy soldiers may reach the point where they would rather surrender than fight. They may signal to you by waving a white flag, by crawling from their positions with arms raised, or by yelling at you to stop firing so that they can give up. The way they signal their desire to surrender may vary, but you must allow them to give up once you receive the signal. It is illegal to fire on enemy soldiers who have thrown down their weapons and offered to surrender. 
United States, Your Conduct in Combat under the Law of War, Publication No. FM 27-2, Headquarters Department of the Army, Washington, November 1984, p. 13.
The US Health Service Manual (1991) notes that the meaning of the words “wounded and sick” is a matter of common sense and good faith. It adds: “It is the act of falling or laying down of arms which constitutes the claim to protection. Only the soldier who is himself seeking to kill may be killed.” 
United States, Field Manual 8–10, Health Service Support in a Theatre of Operations, Department of the Army Headquarters, 1 March 1991, p. A-2.
The US Rules of Engagement for Operation Desert Storm (1991) instructs: “Do not engage anyone who has surrendered, is out of battle due to sickness or wounds, [or] is shipwrecked.” 
United States, Desert Storm – Rules of Engagement, Pocket Card, US Central Command, January 1991, reprinted in Operational Law Handbook, International and Operational Law Department, The Judge Advocate General’s School, United States Army, Charlottesville, Virginia, 1995, pp. 8-7 and 8-8, § A.
The US Operational Law Handbook (1993) prohibits the “killing or wounding of enemy who have surrendered or are incapacitated and incapable of resistance”. 
United States, Operational Law Handbook, JA 422, Center for Law and Military Operations and International Law Division, The Judge Advocate General’s School, United States Army, Charlottesville, Virginia 22903-1781, 1993, p. Q-182(h).
The US Naval Handbook (1995) provides:
Members of the armed forces incapable of participating in combat due to injury or illness may not be the object of attack …
Similarly, shipwrecked persons, whether military or civilian, may not be the object of attack.
Combatants cease to be subject to attack when they have individually laid down their arms to surrender … or when the unit in which they are serving or embarked has surrendered … However, the law of armed conflict does not precisely define when surrender takes effect or how it may be accomplished in practical terms. Surrender involves an offer by the surrendering party (a unit or individual combatant) and an ability to accept on the part of the opponent. The latter may not refuse an offer of surrender when communicated, but that communication must be made at a time when it can be received and properly acted upon – an attempt to surrender in the midst of a hard-fought battle is neither easily communicated nor received. The issue is one of reasonableness. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), §§ 11.4 and 11.7; see also § 8.2.1.
The Handbook also states:
The following acts are representative war crimes:
3. Offenses against the sick and wounded, including killing, wounding, or mistreating enemy forces disabled by sickness or wounds
4. … offenses against combatants who have laid down their arms and surrendered
5. Offenses against the survivors of ships and aircraft lost at sea, including killing, wounding, or mistreating the shipwrecked; and failing to provide for the safety of survivors as military circumstances permit. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 6.2.5(3)-(5).
The US Naval Handbook (2007) states:
Combatants, whether lawful or unlawful, who are hors de combat are those who cannot, do not, or cease to participate in hostilities due to wounds, sickness, shipwreck, surrender, or capture. They may not be intentionally or indiscriminately attacked. They may be detained. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 8.2.3.
The Handbook further states:
Combatants, whether lawful or unlawful, cease to be subject to attack when they have individually laid down their arms and indicate clearly their wish to surrender. The law of armed conflict does not precisely define when surrender takes effect or how it may be accomplished in practical terms. Surrender involves an offer by the surrendering party (a unit or individual combatant) and an ability to accept on the part of the opponent. The latter may not refuse an offer of surrender when communicated, but that communication must be made at a time when it can be received and properly acted upon – an attempt to surrender in the midst of an ongoing battle is neither easily communicated nor received. The issue is one of reasonableness. The mere fact that a combatant or enemy force is retreating or fleeing the battlefield, without some other positive indication of intent, does not constitute an attempt to surrender, even if such combatant or force has abandoned his or its arms or equipment. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 8.2.3.3.
The Handbook also states that examples of war crimes that could be considered as grave breaches of the 1949 Geneva Conventions include:
3. Offenses against the sick and wounded, including killing, wounding, or mistreating enemy forces disabled by sickness or wounds.
4. … offenses against combatants who have laid down their arms and surrendered.
5. Offenses against the survivors of ships and aircraft lost at sea, including killing, wounding, or mistreating the shipwrecked; and failing to provide for the safety of survivors as military circumstances permit. 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 6.2.6(3)–(5).
The US Manual on Detainee Operations (2008) states:
Legal Considerations
a. As a subset of military operations, detainee operations must comply with the law of war during all armed conflicts, however such conflicts are characterized, and in all other military operations …
c. The four Geneva Conventions of 1949 are fully applicable as a matter of international law to all military operations that qualify as international armed conflicts … The principles reflected in these treaties are considered customary international law, binding on all nations during international armed conflict. Although often referred to collectively as the “Geneva Conventions,” the specific treaties are:
(1) [1949] Geneva Convention [I] … This convention provides protection for members of the armed forces and other persons on the battlefield who are no longer actively participating in hostilities as the result of becoming wounded or sick …
(2) [1949] Geneva Convention [II] … This convention requires the … protection of members of the armed forces and other persons at sea who are wounded, sick, or shipwrecked. 
United States, Manual on Detainee Operations, Joint Chiefs of Staff, 30 May 2008, pp. I-2–I-3.
Under the US War Crimes Act (1996), violations of Article 23(c) of the 1907 Hague Regulations are war crimes. 
United States, War Crimes Act, 1996, Section 2441(c)(2).
In the Dostler case before the US Military Commission at Rome in 1945, the accused, the commander of a German army corps, was found guilty of having ordered the shooting of 15 American prisoners of war in violation of the 1907 Hague Regulations and of long-established laws and customs of war. The accused relied on the defence of superior orders based, inter alia, on the Führer’s order of 18 October 1942. This order provided that enemy soldiers participating in commando operations should be given no quarter, but added that these provisions did not apply to enemy soldiers who surrendered and to those who were captured in actual combat within the limits of normal combat activities (offensives, large-scale air or seaborne landings), nor did they apply to enemy troops captured during naval engagements. 
United States, Military Commission at Rome, Dostler case, Judgment, 12 October 1945.
In 1987, the Deputy Legal Adviser of the US Department of State affirmed that “we support the principle that all the wounded, sick, and shipwrecked … not be made the object of attacks”. 
United States, Remarks of Michael J. Matheson, Deputy Legal Adviser, US Department of State, The Sixth Annual American Red Cross-Washington College of Law Conference on International Humanitarian Law: A Workshop on Customary International Law and the 1977 Protocols Additional to the 1949 Geneva Conventions, American University Journal of International Law and Policy, Vol. 2, 1987, p. 423.
In 1991, in response to an ICRC memorandum on the applicability of IHL in the Gulf region, the United States pointed out that its practice was consistent with the prohibition to attack those who had surrendered, as well as defenceless combatants, such as the wounded, sick and shipwrecked. 
United States, Letter from the Department of the Army to the legal adviser of the US armed forces deployed in the Gulf region, 11 January 1991, § 8(J), Report on US Practice, 1997, Chapter 2.8.
In 1992, in its final report to Congress on the conduct of the Gulf War, the US Department of Defense stated:
The law of war obligates a party to a conflict to accept the surrender of enemy personnel and thereafter treat them in accordance with the provisions of the 1949 Geneva Conventions for the Protection of War Victims …
However, there is a gap in the law of war in defining precisely when surrender takes effect or how it may be accomplished in practical terms. Surrender involves an offer by the surrendering party (a unit or an individual soldier) and an ability to accept on the part of his opponent. The latter may not refuse an offer of surrender when communicated, but that communication must be made at a time when it can be received and properly acted upon – an attempt at surrender in the midst of a hard-fought battle is neither easily communicated nor received. The issue is one of reasonableness.
A combatant force involved in an armed conflict is not obliged to offer its opponent an opportunity to surrender before carrying out an attack … In the process [of military operations], Coalition forces continued to accept legitimate Iraqi offers of surrender in a manner consistent with the law of war. The large number of Iraqi prisoners of war is evidence of Coalition compliance with its law of war obligations with regard to surrendering forces. 
United States, Department of Defense, Final Report to Congress on the Conduct of the Persian Gulf War, 10 April 1992, Appendix O, The Role of the Law of War, ILM, Vol. 31, 1992, p. 641.
The report also referred to two incidents during the Gulf War in which there had been allegations that quarter had been denied. The first incident involved an armoured assault on an entrenched position where tanks equipped with earthmoving plough blades were used to breach the trench line and then turned to fill in the trenches and the bunkers. The Department of Defense defended this tactic as consistent with the law of war. It noted that:
In the course of the breaching operations, the Iraqi defenders were given the opportunity to surrender, as indicated by the large number of EPWs [enemy prisoners of war] taken by the division. However, soldiers must make their intent to surrender clear and unequivocal, and do so rapidly. Fighting from fortified emplacements is not a manifestation of an intent to surrender, and a soldier who fights until the very last possible moment assumes certain risks. His opponent either may not see his surrender, may not recognize his actions as an attempt to surrender in the heat and confusion of battle, or may find it difficult (if not impossible) to halt an onrushing assault to accept a soldier’s last-minute effort at surrender. 
United States, Department of Defense, Final Report to Congress on the Conduct of the Persian Gulf War, 10 April 1992, Appendix O, The Role of the Law of War, ILM, Vol. 31, 1992, pp. 642 and 643.
The second incident concerned the attack on Iraqi forces while they were retreating from Kuwait City. The Department of Defense again defended the attack as consistent with the law of war. It noted:
The law of war permits the attack of enemy combatants and enemy equipment at any time, wherever located, whether advancing, retreating or standing still. Retreat does not prevent further attack …
In the case at hand, neither the composition, degree of unit cohesiveness, nor intent of the Iraqi military forces engaged was known at the time of the attack. At no time did any element within the formation offer to surrender. CENTCOM [Central Command] was under no law of war obligation to offer the Iraqi forces an opportunity to surrender before the attack. 
United States, Department of Defense, Final Report to Congress on the Conduct of the Persian Gulf War, 10 April 1992, Appendix O, The Role of the Law of War, ILM, Vol. 31, 1992, pp. 643 and 644.
The Report on US Practice states:
The opinio juris of the United States is that quarter must not be refused to an enemy who communicates an offer to surrender under circumstances permitting that offer to be understood and acted upon by U.S. forces. A combatant who appears merely incapable or unwilling to fight, e.g., because he has lost his weapon or is retreating from the battle, but who has not communicated an offer to surrender, is still subject to attack. (Persons hors de combat due to wounds, sickness or shipwreck must of course be respected in all circumstances, in accordance with the First and Second Geneva Conventions of 1949). 
Report on US Practice, 1997, Chapter 2.1.