Related Rule
United States of America
Practice Relating to Rule 46. Orders or Threats That No Quarter Will Be Given
The US Field Manual (1956) provides: “It is especially forbidden … to declare that no quarter will be given.” 
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, § 28.
The US Manual for Military Commissions (2007), Part IV, Crimes and Elements, includes in the list of crimes triable by military commissions:
DENYING QUARTER.
a. Text. “Any person subject to this chapter who, with effective command or control over subordinate groups, declares, orders, or otherwise indicates to those groups that there shall be no survivors or surrender accepted, with the intent to threaten an adversary or to conduct hostilities such that there would be no survivors or surrender accepted, shall be punished as a military commission under this chapter may direct.”
b. Elements.
(1) The accused declared, ordered, or otherwise indicated that there shall be no survivors or surrender accepted;
(2) The accused thereby intended to threaten an adversary or to conduct hostilities such that there would be no survivors or surrender accepted;
(3) It was foreseeable that circumstances would be such that a practicable and reasonable ability to accept surrender would exist;
(4) The accused was in a position of effective command or control over the subordinate forces to which the declaration or order was directed; and
(5) The conduct took place in the context of and was associated with armed conflict.
c. Maximum punishment. Confinement for life. 
United States, Manual for Military Commissions, published in implementation of the Military Commissions Act of 2006, 10 U.S.C. §§ 948a, et seq., 18 January 2007, Part IV, § 6(6), p. IV-6.
The US Manual for Military Commissions (2010), Part IV, Crimes and Elements, includes in the list of crimes triable by military commissions:
DENYING QUARTER.
a. Text. “Any person subject to this chapter who, with effective command or control over subordinate groups, declares, orders, or otherwise indicates to those groups that there shall be no survivors or surrender accepted, with the intent to threaten an adversary or to conduct hostilities such that there would be no survivors or surrender accepted, shall be punished as a military commission under this chapter may direct.”
b. Elements.
(1) The accused declared, ordered, or otherwise indicated that there shall be no survivors or surrender accepted;
(2) The accused thereby intended to threaten an adversary or to conduct hostilities such that there would be no survivors or surrender accepted;
(3) It was foreseeable that circumstances would be such that a practicable and reasonable ability to accept surrender would exist;
(4) The accused was in a position of effective command or control over the subordinate forces to which the declaration or order was directed; and
(5) The conduct took place in the context of and was associated with hostilities.
c. Maximum punishment. Confinement for life. 
United States, Manual for Military Commissions, published in implementation of Chapter 47A of Title 10, United States Code, as amended by the Military Commissions Act of 2009, 10 U.S.C, §§ 948a, et seq., 27 April 2010, § 5(6), p. IV-6.
Under the US War Crimes Act (1996), violations of Article 23(d) of the 1907 Hague Regulations are war crimes. 
United States, War Crimes Act, 1996, Section 2441(c)(2).
The US Military Commissions Act (2006), passed by Congress following the Supreme Court’s decision in Hamdan v. Rumsfeld in 2006, amends Title 10 of the United States Code as follows:
§ 950v. Crimes triable by military commissions
“ …
“(b) OFFENSES.—The following offenses shall be triable by military commission under this chapter at any time without limitation:
“ …
“(6) DENYING QUARTER.—Any person subject to this chapter who, with effective command or control over subordinate groups, declares, orders, or otherwise indicates to those groups that there shall be no survivors or surrender accepted, with the intent to threaten an adversary or to conduct hostilities such that there would be no survivors or surrender accepted, shall be punished as a military commission under this chapter may direct. 
United States, Military Commissions Act, 2006, Public Law 109-366, Chapter 47A of Title 10 of the United States Code, 17 October 2006, p. 120 Stat. 2626, § 950v(b)(6).
The US Military Commissions Act (2009) amends Chapter 47A of Title 10 of the United States Code as follows:
§ 950t. Crimes triable by military commission
“The following offenses shall be triable by military commission under this chapter at any time without limitation:
“ …
“(6) DENYING QUARTER.—Any person subject to this chapter who, with effective command or control over subordinate groups, declares, orders, or otherwise indicates to those groups that there shall be no survivors or surrender accepted, with the intent to threaten an adversary or to conduct hostilities such that there would be no survivors or surrender accepted, shall be punished as a military commission under this chapter may direct. 
United States, Military Commissions Act, 2009, § 950t(6).
In the Thiele case before the US Military Commission at Augsburg in 1945, the accused, a German army lieutenant, was convicted of having ordered the killing of an American prisoner of war. 
United States, Military Commission at Augsburg, Thiele case, Judgment, 13 June 1945.
In the Von Leeb case (The German High Command Trial) before the US Military Tribunal at Nuremberg in 1948, the accused, former high-ranking officers in the German army and navy, were charged, inter alia, with war crimes against enemy belligerents and prisoners of war for having unlawfully directed that certain enemy troops be refused quarter and that certain captured members of the military forces of nations at war with Germany be summarily executed. In its judgment, the Tribunal stated: “in the course of the war, many Allied soldiers who had surrendered to the Germans were shot immediately, often as a matter of deliberate, calculated policy”. It added that “the murder of Commandos or captured airmen … were the result of direct orders circulated through the highest official channels”. It also referred to Hitler’s order of 18 October 1942 whereby no quarter should be granted to members of Allied commando units, stating that “this order was criminal on its face. It simply directed the slaughter of these ‘sabotage’ troops.” 
United States, Military Tribunal at Nuremberg, Von Leeb case (The German High Command Trial), Judgment, 28 October 1948.
In 1987, the Deputy Legal Adviser of the US Department of State affirmed: “We support the principle that no order be given that there shall be no survivors nor an adversary be threatened with such an order or hostilities be conducted on that basis.” 
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. 425.
In 1991, in response to an ICRC memorandum on the applicability of IHL in the Gulf region, the United States commented that its practice was consistent with the prohibition on ordering that there shall be no survivors. 
United States, Letter from the Department of the Army to the legal adviser of the US Army 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 that Article 23(d) of the 1907 Hague Regulations “prohibits the denial of quarter, that is the refusal to accept an enemy’s 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, p. 641.