Related Rule
United States of America
Practice Relating to Rule 2. Violence Aimed at Spreading Terror among the Civilian Population
The US Air Force Pamphlet (1976) states: “Acts or threats of violence which have the primary object of spreading terror among the civilian population are prohibited.” 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 5-3(a)(1)(a).
The US Naval Handbook (1995) states: “The civilian population as such, as well as individual civilians, may not be the object of attack or of threats or acts of intentional terrorization.” 
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), § 11.3.
The Handbook also states that carrying out a “bombardment, the sole purpose of which is to attack and terrorize the civilian population” is an example of a war crime. 
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
The US Manual for Military Commissions (2007), Part IV, Crimes and Elements, includes in the list of crimes triable by military commissions:
TERRORISM.
a. Text. “Any person subject to this chapter who intentionally kills or inflicts great bodily harm on one or more protected persons, or intentionally engages in an act that evinces a wanton disregard for human life, in a manner calculated to influence or affect the conduct of government or civilian population by intimidation or coercion, or to retaliate against government conduct, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct.”
b. Elements.
(1) The accused intentionally killed or inflicted great bodily harm on one or more protected persons or engaged in an act that evinced a wanton disregard for human life;
(2) The accused did so in a manner calculated to influence or affect the conduct of government or civilian population by intimidation or coercion, or to retaliate against government conduct; and
(3) The killing, harm or wanton disregard for human life took place in the context of and was associated with armed conflict.
c. Comment.
(1) This offense includes the concept of causing death or bodily harm, even if indirectly.
(2) The requirement that the conduct be wrongful for this crime necessitates that the conduct establishing this offense not constitute an attack against a lawful military objective undertaken by military forces of a State in the exercise of their official duties.
d. Maximum Punishment. Death, if the death of any person occurs as a result of the terrorist act. Otherwise, confinement for life.
PROVIDING MATERIAL SUPPORT FOR TERRORISM.
a. Text. “Any person subject to this chapter who provides material support or resources, knowing or intending that they are to be used in preparation for, or in carrying out, an act of terrorism (as set forth in paragraph (24)), or who intentionally provides material support or resources to an international terrorist organization engaged in hostilities against the United States, knowing that such organization has engaged or engages in terrorism (as so set forth), shall be punished as a military commission under this chapter may direct.”
b. Elements. The elements of this offense can be met either by meeting (i) all of the elements in A, or (ii) all of the elements in B, or (iii) all of the elements in both A and B:
A. (1) The accused provided material support or resources to be used in preparation for, or in carrying out, an act of terrorism (as set forth in paragraph (24));
(2) The accused knew or intended that the material support or resources were to be used for those purposes; and
(3) The conduct took place in the context of and was associated with an armed conflict.
or
B. (1) The accused provided material support or resources to an international terrorist organization engaged in hostilities against the United States;
(2) The accused intended to provide such material support or resources to such an international terrorist organization;
(3) The accused knew that such organization has engaged or engages in terrorism; and
(4) The conduct took place in the context of and was associated with an armed conflict.
c. Definition. “Material support or resources” means any property, tangible or intangible, or service, including currency or monetary instruments or financial securities, financial services, lodging, training, expert advice or assistance, safehouses, false documentation or identification, communications equipment, facilities, weapons, lethal substances, explosives, personnel (one or more individuals who may be or include oneself), and transportation, except medicine or religious materials.
d. 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(24) and (25), pp. IV-17 and IV-18.
The US Naval Handbook (2007) states: “Bombardment for the sole purpose of terrorizing the civilian population is prohibited.” 
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, § 8.3; see also § 8.9.1.2.
The Handbook also states that examples of war crimes that could be considered as grave breaches of the 1949 Geneva Conventions include carrying out a “bombardment, the sole purpose of which is to attack and terrorize the civilian population”. 
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(6).
The US Manual for Military Commissions (2010), Part IV, Crimes and Elements, includes in the list of crimes triable by military commissions:
(24) TERRORISM.
a. Text. “Any person subject to this chapter who intentionally kills or inflicts great bodily harm on one or more protected persons, or intentionally engages in an act that evinces a wanton disregard for human life, in a manner calculated to influence or affect the conduct of government or civilian population by intimidation or coercion, or to retaliate against government conduct, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct.”
b. Elements.
(1) The accused intentionally killed or inflicted great bodily harm on one or more protected persons or engaged in an act that evinced a wanton disregard for human life;
(2) The accused did so in a manner calculated to influence or affect the conduct of government or civilian population by intimidation or coercion, or to retaliate against government conduct; and
(3) The killing, harm or wanton disregard for human life took place in the context of and was associated with hostilities.
c. Comment.
(1) This offense includes the concept of causing death or bodily harm, even if indirectly.
(2) The requirement that the conduct be wrongful for this crime necessitates that the conduct establishing this offense not constitute an attack against a lawful military objective undertaken by military forces of a State in the exercise of their official duties
d. Maximum Punishment. Death, if the death of any person occurs as a result of the terrorist act. Otherwise, confinement for life.
(25) PROVIDING MATERIAL SUPPORT FOR TERRORISM.
a. Text. “Any person subject to this chapter who provides material support or resources, knowing or intending that they are to be used in preparation for, or in carrying out, an act of terrorism (as set forth in paragraph (24) of this section), or who intentionally provides material support or resources to an international terrorist organization engaged in hostilities against the United States, knowing that such organization has engaged or engages in terrorism (as so set forth), shall be punished as a military commission under this chapter may direct.”
b. Elements. The elements of this offense can be met either by meeting (i) all of the elements in A, or (ii) all of the elements in B, or (iii) all of the elements in both A and B:
A. (1) The accused provided material support or resources to be used in preparation for, or in carrying out, an act of terrorism (as set forth in paragraph (24));
(2) The accused knew or intended that the material support or resources were to be used for those purposes; and
(3) The conduct took place in the context of and was associated with hostilities.
B. (1) The accused provided material support or resources to an international terrorist organization engaged in hostilities against the United States;
(2) The accused intended to provide such material support or resources to such an international terrorist organization;
(3) The accused knew that such organization has engaged or engages in terrorism; and
(4) The conduct took place in the context of and was associated with hostilities.
c. Definition. “Material support or resources” means any property, tangible or intangible, or service, including currency or monetary instruments or financial securities, financial services, lodging, training, expert advice or assistance, safehouses, false documentation or identification, communications equipment, facilities, weapons, lethal substances, explosives, personnel (one or more individuals who may be or include oneself), and transportation, except medicine or religious materials.
d. 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(24) and (25), pp. IV-19 and IV-20.
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:
“ …
“(24) TERRORISM. – Any person subject to this chapter who intentionally kills or inflicts great bodily harm on one or more protected persons, or intentionally engages in an act that evinces a wanton disregard for human life, in a manner calculated to influence or affect the conduct of government or civilian population by intimidation or coercion, or to retaliate against government conduct, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct.
“(25) Providing material support for terrorism. –
“(A) OFFENSE. – Any person subject to this chapter who provides material support or resources, knowing or intending that they are to be used in preparation for, or in carrying out, an act of terrorism (as set forth in paragraph (24)), or who intentionally provides material support or resources to an international terrorist organization engaged in hostilities against the United States, knowing that such organization has engaged or engages in terrorism (as so set forth), shall be punished as a military commission under this chapter may direct.
“(B) MATERIAL SUPPORT OR RESOURCES DEFINED. – In this paragraph, the term ‘material support or resources’ has the meaning given that term in section 2339A(b) of title 18. 
United States, Military Commissions Act, 2006, Public Law 109-366, Chapter 47A of Title 10 of the United States Code, 17 October 2006, pp. 120 Stat. 2629 and 2630, § 950v(b)(24) and (25).
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:
“ …
“(24) Terrorism.—Any person subject to this chapter who intentionally kills or inflicts great bodily harm on one or more protected persons, or intentionally engages in an act that evinces a wanton disregard for human life, in a manner calculated to influence or affect the conduct of government or civilian population by intimidation or coercion, or to retaliate against government conduct, shall be punished, if death results to one or more of the victims, by death or such other punishment as a military commission under this chapter may direct, and, if death does not result to any of the victims, by such punishment, other than death, as a military commission under this chapter may direct.
“(25) PROVIDING MATERIAL SUPPORT FOR TERRORISM.—
“(A) Offense.—Any person subject to this chapter who provides material support or resources, knowing or intending that they are to be used in preparation for, or in carrying out, an act of terrorism (as set forth in paragraph (24) of this section), or who intentionally provides material support or resources to an international terrorist organization engaged in hostilities against the United States, knowing that such organization has engaged or engages in terrorism (as so set forth), shall be punished as a military commission under this chapter may direct.
“(B) Material support of resources defined.—In this paragraph, the term ‘material support or resources’ has the meaning given that term in section 2339A(b) of title 18. 
United States, Military Commissions Act, 2009, § 950t(24) and (25).
The Act also states:
§ 950p. Definitions; construction of certain offenses; common circumstances
“(a) DEFINITIONS.—In this subchapter:
“ …
“(2) The term ‘protected person’ means any person entitled to protection under one or more of the Geneva Conventions, including civilians not taking an active part in hostilities … 
United States, Military Commissions Act, 2009, § 950p(a)(2).
In 1987, the Deputy Legal Adviser of the US Department of State stated: “We support the principle that the civilian population as such, as well as individual citizens, not be the object of acts or threats of violence the primary purpose of which is to spread terror among them.” 
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. 426.
In 1991, in response to an ICRC memorandum on the applicability of IHL in the Gulf region, the US Department of the Army pointed out that US practice was consistent with the prohibition on acts or threats of violence the main purpose of which was to spread terror among the civilian population. 
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 1.4.
In 1994, in a document concerning human rights practices in Bosnia and Herzegovina, the US Department of State noted that the Bosnian Serb armed militia employed rape as a tool of war to terrorize and uproot populations. 
United States, Department of State, Bosnia-Herzegovina Human Rights Practice, 1993, 31 January 1994, p. 2.