Related Rule
United States of America
Practice Relating to Rule 145. Reprisals
The US Field Manual (1956) states:
(a) Definition. Reprisals are acts of retaliation in the form of conduct which would otherwise be unlawful, resorted to by one belligerent against enemy personnel or property for acts of warfare committed by the other belligerent in violation of the law of war, for the purpose of enforcing future compliance with the recognized rules of civilized warfare. For example, the employment by a belligerent of a weapon the use of which is normally precluded by the law of war would constitute a lawful reprisal for intentional mistreatment of prisoners of war held by the enemy.
(c) Against Whom Permitted. Reprisals against the persons or property of prisoners of war, including the wounded and sick, and protected civilians are forbidden. Collective penalties and punishment of prisoners of war and protected civilians are likewise prohibited. However, reprisals may still be visited on enemy troops who have not yet fallen into the hands of the forces making the reprisals.
(d) When and how employed. Reprisals are never adopted merely for revenge, but only as an unavoidable last resort to induce the enemy to desist from unlawful practices. They should never be employed by individual soldiers except by direct orders of a commander, and the latter should give such orders only after careful inquiry into the alleged offense. The highest accessible military authority should be consulted unless immediate action is demanded, in which event a subordinate commander may order appropriate reprisals upon his own initiative. Ill-considered action may subsequently be found to have been wholly unjustified and will subject the responsible officer himself to punishment for a violation of the law of war. On the other hand, commanding officers must assume responsibility for retaliative measures when an unscrupulous enemy leaves no other recourse against the repetition of unlawful acts.
(f) Procedure. The rule requiring careful inquiry into the real occurrence will always be followed unless the safety of the troops requires immediate drastic action and the persons who actually committed the offence cannot be ascertained.
(g) Hostages. The taking of hostages is forbidden. The taking of prisoners by way of reprisal for acts previously committed (so-called “reprisal prisoners”) is likewise forbidden. 
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, § 497(a), (d), (f) and (g).
The US Air Force Pamphlet (1976) states:
In order to be considered as a reprisal, an act must have the following characteristics when employed:
(1) It must respond to grave and manifestly unlawful acts, committed by an adversary government, its military commanders, or combatants for whom the adversary is responsible.
(2) It must be for the purpose of compelling the adversary to observe the law of armed conflict. Reprisals cannot be undertaken for revenge, spite or punishment. Rather, they are directed against an adversary in order to induce him to refrain from further violations of the law of armed conflict. Thus, reprisals serve as an ultimate legal sanction or law enforcement mechanism. Above all, they are justifiable only to force an adversary to stop its extra-legal activity. If, for example, one party to an armed conflict commits a breach of law but follows that violation with an expression of regret and promise that it will not be repeated, and even takes steps to punish those immediately responsible, then any action taken by another party to “right” the situation cannot be justified as a lawful reprisal.
(3) There must be reasonable notice that reprisals will be taken. What degree of notice is required will depend upon the particular circumstances of each case. Notice is normally given after the violation but may, in appropriate circumstances, predate the violation. An example of notice is an appeal to the transgressor to cease its offending conduct and punish those responsible. Thus, such an appeal may serve both as a plea for compliance and a notice to the adversary that reprisals will be undertaken. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(c)(1), (2) and (3).
The Pamphlet also states:
If an act is a lawful reprisal, then as a legal measure it cannot lawfully be the excuse for a counter-reprisal. Under international law, as under domestic law, there can be no reprisal against a lawful reprisal. In fact, reprisals have frequently led to counter-reprisals, and the escalation of the conflicts through reprisals and counter-reprisals is one of the reasons for decline in the use of reprisals. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(a).
The Pamphlet further states:
[The reprisal] must be publicized. Since reprisals are undertaken to induce an adversary’s compliance with the recognized rules of armed conflict, any action taken as a reprisal must be announced as a reprisal and publicized so that the adversary is aware of its obligation to abide by the law. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(c)(7).
The US Air Force Commander’s Handbook (1980) states:
A reprisal is an otherwise illegal act committed to persuade the enemy to cease some illegal activity on their part …
(1) While it is both lawful and proper to plan reprisal actions, as a practical matter, reprisals are often subject to abuse and merely result in escalation of the conflict.
(3) In most twentieth century conflicts, the United States has, as a matter of national policy, chosen not to carry out reprisals against the enemy, both because of the potential for escalation and because it is generally in our national interest to follow the law even if the enemy does not.
(4) The term “reprisal” is sometimes used to refer to any act of retaliation between the parties to a conflict. In law, however, the term should be limited to otherwise illegal acts done in reply to prior illegal acts of the enemy, as described in this paragraph. 
United States, Air Force Pamphlet 110-34, Commander’s Handbook on the Law of Armed Conflict, Judge Advocate General, US Department of the Air Force, 25 July 1980, § 8-4(b).
The US Naval Handbook (1995) states:
A reprisal is an enforcement measure under the law of armed conflict consisting of an act which would otherwise be unlawful but which is justified as a response to the unlawful acts of an enemy. The sole purpose of a reprisal is to induce the enemy to cease its illegal activity and to comply with the law of armed conflict. 
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), § 6.2.3.
The Handbook further states:
To be valid, a reprisal action must conform to the following criteria:
2. It must respond to illegal acts of warfare committed by an adversary government, its military commanders, or combatants for which the adversary is responsible. Anticipatory reprisal is not authorized.
4. Its purpose must be to cause the enemy to cease its unlawful activity. Therefore, acts taken in reprisal should be brought to the attention of the enemy in order to achieve maximum effectiveness. Reprisal must never be taken for revenge. 
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), § 6.2.3.1.
The Handbook also provides:
Although reprisal is lawful when the foregoing requirements are met, there is always the risk that it will trigger retaliatory escalation (counter-reprisals) by the enemy. The United States has historically been reluctant to resort to reprisal for just this reason. 
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), § 6.2.3.3.
The Annotated Supplement to the US Naval Handbook (1997) states:
A careful inquiry by the injured belligerent into the alleged violating conduct should precede the authorization of any reprisal measure. This is subject to the important qualification that, in certain circumstances, an offended belligerent is justified in taking immediate reprisals against illegal acts of warfare, particularly in those situations where the safety of his armed forces would clearly be endangered by a continuance of the enemy’s illegal acts. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.1, footnote 38.
The Annotated Supplement also states:
Acts taken in reprisal may also be brought to the attention of neutrals if necessary to achieve maximum effectiveness. Since reprisals are undertaken to induce an adversary’s compliance with the recognized rules of armed conflict, any action taken as a reprisal must be announced as a reprisal and publicized so that the adversary is aware of its obligation to abide by the law and to ensure that the reprisal action is not, itself, viewed as an unlawful act. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.1, footnote 40.
The Annotated Supplement further states: “If an act is a lawful reprisal, it cannot lawfully be a basis for a counter-reprisal. Under international law, there can be no reprisal against a lawful reprisal.” 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.1, footnote 43.
In another note, the Annotated Supplement states: “Although it is not prohibited to issue … an order [that no quarter will be given or that no prisoners will be taken] as a reprisal, this form of reprisal offers little military advantage.” 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 11.7, footnote 45.
The US Naval Handbook (2007) states:
If one nation violates the law, it may expect that others will reciprocate. Consequently, failure to comply with international law ordinarily involves greater political and economic costs than does observance. In short, nations comply with international law because it is in their interest to do so. 
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, p. 20.
The Handbook also states:
6.2.4 Reprisal
A belligerent reprisal is an enforcement measure under the law of armed conflict consisting of an act that would otherwise be unlawful but which is justified as a response to the previous unlawful acts of an enemy. The sole purpose of a reprisal is to induce the enemy to cease its illegal activity and to comply with the law of armed conflict in the future. Reprisals may be taken against enemy armed forces, enemy civilians other than those in occupied territory, and enemy property.
6.2.4.1 Requirements for Reprisal
To be valid, a reprisal action must conform to the following criteria:
2. It must respond to illegal acts of warfare committed by an adversary government, its military commanders, or combatants for which the adversary is responsible. Anticipatory reprisal is not authorized.
4. Its purpose must be to cause the enemy to cease its unlawful activity. Therefore, acts taken in reprisal should be brought to the attention of the enemy in order to achieve maximum effectiveness. Reprisal must never be taken for revenge. 
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, §§ 6.2.4 and 6.2.4.1.
In the List case (The Hostages Trial) in the late 1947/48, the US Military Tribunal at Nuremberg held: “A reprisal is a response to an enemy’s violation of the laws of war which would otherwise be a violation on one’s own side.” 
United States, Military Tribunal at Nuremberg, List (The Hostages Trial) case, 8 July 1947–19 February 1948.
As to the difference between the taking of hostages and measures of reprisal, the Tribunal stated:
Where innocent individuals are seized and punished for a violation of the laws of war which has already occurred, no question of hostages is involved. It is nothing more than the infliction of a reprisal. Throughout the evidence in the present case, we find the term hostage applied where a reprisal only was involved.
However, it stated: “The term ‘reprisal prisoners’ will be considered as those individuals who are taken from the civilian population to be killed in retaliation for offences committed by unknown persons within the occupied area.” It also stated:
Where legality of action is absent, the shooting of innocent members of the population as a measure of reprisal is not only criminal but it has the effect of destroying the basic relationship between the occupant and the population. Such a condition can progressively degenerate into a reign of terror. Unlawful reprisals may bring on counter reprisals and create an endless cycle productive of chaos and crime. To prevent a distortion of the right into a barbarous method of repression, International Law provides a protective mantle against the abuse of the right. 
United States, Military Tribunal at Nuremberg, List (The Hostages Trial) case, 8 July 1947–19 February 1948.
In 1980, in a footnote to a memorandum of law on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, a legal adviser of the US Department of State noted that “reprisals are permitted under the laws of war only for the limited purpose of compelling the other belligerent to observe the laws of war”. 
United States, Department of State, Memorandum of law by a Legal Adviser on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, 9 April 1980, reprinted in Marian Nash Leich, Digest of United States Practice in International Law, 1980, Department of State Publication 9610, Washington, D.C., December 1986, pp. 1034 and 1041, footnote 38.
In 1987, a Legal Adviser of the US Department of State, explaining “the position of the United States on current law of war agreements”, stated with regard to Article 51 of the 1977 Additional Protocol I: “[This provision] prohibits any reprisal attacks against the civilian population, that is, attacks that would otherwise be forbidden but that are in response to the enemy’s own violations of the law and are intended to deter future violations.” 
United States, Remarks of Judge Abraham D. Sofaer, 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, 22 January 1987, American University Journal of International Law and Policy, Vol. 2, 1987, p. 469.
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States stated:
For the purpose of the law of armed conflict, reprisals are lawful acts of retaliation in the form of conduct that would otherwise be unlawful, resorted to by one belligerent in response to violations of the law of war by another belligerent. Such reprisals would be lawful if conducted in accordance with the applicable principles governing belligerent reprisals. Specifically, the reprisals must be taken with the intent to cause the enemy to cease violations of the law of armed conflict … As in the case of other requirements of the law of armed conflict, a judgment about compliance of any use of nuclear weapons with these requirements would have to be made on the basis of the actual circumstances in each case, and could not be made in advance or in the abstract. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 30.
The US Field Manual (1956) states:
Priority to Other Remedies. Other measures of securing compliance with the law of war should normally be exhausted before resort is had to reprisals. This course should be pursued unless the safety of the troops requires immediate drastic action and the persons who actually committed the offences cannot be secured. Even when appeal to the enemy for redress has failed, it may be a matter of policy to consider, before resorting to reprisals, whether the opposing forces are not more likely to be influenced by a steady adherence to the law of war on the part of their adversary. 
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, § 497(b).
The manual adds: “Reprisals are never adopted merely for revenge, but only as an unavoidable last resort to induce the enemy to desist from unlawful practices.” 
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, § 497(d).
The US Air Force Pamphlet (1976), in explaining reprisals, states:
(a) The action is taken in the last resort, in order to prevent the adversary from behaving illegally in the future.
(c) In order to be considered a reprisal, an act must have the following characteristics when employed:
(3) There must be reasonable notice that reprisals will be taken. What degree of notice is required will depend upon the particular circumstances of each case. Notice is normally given after the violation but may, in appropriate circumstances, predate the violation. An example of notice is an appeal to the transgressor to cease its offending conduct and punish those responsible. Thus, such an appeal may serve both as a plea for compliance and a notice to the adversary that reprisals will be undertaken.
(4) Other reasonable means to secure compliance must be attempted. The victim of a violation in order to justify taking a reprisal must first exhaust other reasonable means of securing compliance. This may involve appeals or notice … Finally, even if an appeal or other methods fail, reprisals should not be undertaken automatically since there are various other factors governing their employment. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(a) and (c).
The US Air Force Commander’s Handbook (1980) states: “The taking of reprisals should be preceded by a request for redress of the wrong.” 
United States, Air Force Pamphlet 110-34, Commander’s Handbook on the Law of Armed Conflict, Judge Advocate General, US Department of the Air Force, 25 July 1980, § 8-4(b)(2).
The US Naval Handbook (1995) provides:
To be valid, a reprisal action must conform to the following criteria:
3. When circumstances permit, reprisal must be preceded by a demand for redress by the enemy of his unlawful acts.
5. Reprisal must only be used as a last resort when other enforcement measures have failed or would be of no avail. 
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), § 6.2.3.1.
The US Naval Handbook (2007) states:
To be valid, a reprisal action must conform to the following criteria:
3. When circumstances permit, reprisal must be preceded by a demand for redress by the enemy of its unlawful acts.
5. Reprisal must only be used as a last resort when other enforcement measures have failed or would be of no avail. 
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, § 6.2.4.1.
In its judgment in the List case (The Hostages Trial) in the late 1940s, the US Military Tribunal at Nuremberg, discussing the taking of hostages in occupied territories, noted: “The occupant is required to use every available method to secure order and tranquillity before resort may be had to the taking and execution of hostages.” However, the Tribunal had previously stated:
Where innocent individuals are seized and punished for a violation of the laws of war which has already occurred, no question of hostages is involved. It is nothing more than the infliction of a reprisal. Throughout the evidence in the present case, we find the term hostage applied where a reprisal only was involved. 
United States, Military Tribunal at Nuremberg, List case (The Hostages Trial), Judgment, 8 July 1947–19 February 1948.
In 1980, in a footnote to a memorandum of law on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, a legal adviser of the US Department of State stated: “Reprisals are permitted under the laws of war … only after other means of achieving this objective [i.e. “the limited purpose of compelling the other belligerent to observe the laws of war”] have been exhausted (including diplomatic protest).” 
United States, Department of State, Memorandum of law by a Legal Adviser on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, 9 April 1980, reprinted in Marian Nash Leich, Digest of United States Practice in International Law, 1980, Department of State Publication 9610, Washington, D.C., December 1986, pp. 1034 and 1041, footnote 38.
In a written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States stated:
Reprisals would be lawful if conducted in accordance with the applicable principles governing belligerent reprisals. Specifically … other means of securing compliance [of the enemy with the law of armed conflict] should be exhausted … As in the case of other requirements of the law of armed conflict, a judgment about compliance of any use of nuclear weapons with these requirements would have to be made on the basis of the actual circumstances in each case, and could not be made in advance or in the abstract. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 30.
The US Field Manual (1956) states:
Form of Reprisal. What kinds of acts should be resorted to as reprisals is a matter for consideration by the injured party. Acts done by way of reprisals must not, however, be excessive. They must bear reasonable relation to the degree of violation committed by the enemy. 
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, § 497(e).
The US Air Force Pamphlet (1976) states:
A reprisal must be proportional to the original violation. Although a reprisal need not conform in kind to the same type of acts complained of (bombardment for bombardment, weapon for weapon) it may not significantly exceed the adversary’s violation either in violence or effect. Effective but disproportionate reprisals cannot be justified by the argument that only an excessive response will forestall further transgressions. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(c)(6).
The US Naval Handbook (1995) provides: “To be valid, a reprisal action must conform to the following criteria: … 6. Each reprisal must be proportional to the original violation.” 
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), § 6.2.3.1.
The Annotated Supplement to the US Naval Handbook (1997) states:
This rule [that a reprisal must be proportional to the original violation] is not of strict equivalence because the reprisal will usually be somewhat greater that the initial violation that gave rise to it. However, care must be taken that the extent of the reprisal is measured by some degree of proportionality and not solely by effectiveness. Effective but disproportionate reprisals cannot be justified by the argument that only an excessive response will forestall a further transgression … The acts resorted to by way of reprisal need not conform in kind to those complained of by the injured belligerent. The reprisal action taken may be quite different from the original act which justified it, but should not be excessive or exceed the degree of harm required to deter the enemy from continuance of his initial unlawful conduct. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.1, footnote 43.
The US Naval Handbook (2007) states: “To be valid, a reprisal action must conform to the following criteria: … 6. Each reprisal must be proportional to the original violation.” 
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, § 6.2.4.1.
In its judgment in the List case (The Hostages Trial) in the late 1940s, the US Military Tribunal at Nuremberg stated: “It is a fundamental rule that a reprisal may not exceed the degree of the criminal act it is designed to correct. Where an excess is knowingly indulged, it in turn is criminal and may be punished.” 
United States, Military Tribunal at Nuremberg, List case (The Hostages Trial), Judgment, 8 July 1947–19 February 1948.
In 1980, in a footnote to a memorandum of law on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, a legal adviser of the US Department of State noted: “Reprisals are permitted under the laws of war … only in proportion to the original violations.” 
United States, Department of State, Memorandum of law by a Legal Adviser on the “Reported Use of Chemical Agents in Afghanistan, Laos, and Kampuchea”, 9 April 1980, reprinted in Marian Nash Leich, Digest of United States Practice in International Law, 1980, Department of State Publication 9610, Washington, D.C., December 1986, pp. 1034 and 1041, footnote 38.
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States stated:
Reprisals would be lawful if conducted in accordance with the applicable principles governing belligerent reprisals. Specifically … the reprisals must be proportionate to the violations [of the law of armed conflict by the enemy] … As in the case of other requirements of the law of armed conflict, a judgment about compliance of any use of nuclear weapons with these requirements would have to be made on the basis of the actual circumstances in each case, and could not be made in advance or in the abstract. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 30.
The US Field Manual (1956) stipulates:
When and how employed. Reprisals are never adopted merely for revenge, but only as an unavoidable last resort to induce the enemy to desist from unlawful practices. They should never be employed by individual soldiers except by direct orders of a commander, and the latter should give such orders only after careful inquiry into the alleged offence. The highest accessible military authority should be consulted unless immediate action is demanded, in which event a subordinate commander may order appropriate reprisals upon his own initiative. Ill-considered action may subsequently be found to have been wholly unjustified and will subject the responsible officer himself to punishment for a violation of the law of war. On the other hand, commanders must assume responsibility for retaliative measures when an unscrupulous enemy leaves no other recourse against repetition of unlawful acts. 
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, § 497(d).
The US Air Force Pamphlet (1976) states:
In order to be considered a reprisal, an act must have the following characteristics when employed:
(8) It must be authorized by national authorities at the highest political level and entails full state responsibility. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 10-7(c)(8).
The US Air Force Commander’s Handbook (1980) states: “A decision to violate the law in reprisal for enemy violations must be taken at the highest levels of the US government”. 
United States, Air Force Pamphlet 110-34, Commander’s Handbook on the Law of Armed Conflict, Judge Advocate General, US Department of the Air Force, 25 July 1980, § 1-3(a)(2).
The Handbook further states: “Only the national command authorities may authorize the execution of reprisals or other reciprocal violations of the law of armed conflict by US armed forces.” 
United States, Air Force Pamphlet 110-34, Commander’s Handbook on the Law of Armed Conflict, Judge Advocate General, US Department of the Air Force, 25 July 1980, § 8-4(b)(2).
The US Instructor’s Guide (1985) states: “The individual soldier must never decide to make a reprisal. The decision to make a reprisal must be made at the highest command level.” 
United States, Instructor’s Guide – The Law of War, Headquarters Department of the Army, Washington, April 1985, p. 27.
The US Naval Handbook (1995) provides: “To be valid, a reprisal action must conform to the following criteria: 1. Reprisal must be ordered by an authorized representative of the belligerent government.” It adds: “The President alone may authorize the taking of reprisal action by U.S. Forces.” 
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), §§ 6.2.3.1 and 6.2.3.3.
The Annotated Supplement to the US Naval Handbook (1997), in a part dealing with the necessity for the United States that the President alone may authorize the taking of reprisal action by US forces, states that there is “always the risk that it will trigger retaliatory escalation (counter-reprisals) by the enemy”. It adds:
Other factors which governments will usually consider before taking of reprisals include the following:
1. Reprisals may have an adverse influence on the attitudes of governments not participating in an armed conflict.
2. Reprisals may only strengthen enemy morale and underground resistance.
3. Reprisals may only lead to counter-reprisals by an enemy, in which case the enemy’s ability to retaliate is an important factor.
4. Reprisals may render enemy resources less able to contribute to the rehabilitation of an area after the cessation of hostilities.
5. The threat of reprisals may be more effective than their actual use.
6. Reprisals, to be effective, should be carried out speedily and should be kept under control. They may be ineffective if random, excessive, or prolonged.
7. In any event, the decision to employ reprisals will generally be reached as a matter of strategic policy. The immediate advantage sought must be weighed against the possible long-range military and political consequences.
In addition to the legal requirements which regulate resort to reprisals, there are various practical factors which governments will consider before taking reprisals. For example, when appeal to the enemy for redress has failed, it may be a matter of policy to consider before resorting to reprisals, whether the opposing forces are not more likely to be influenced by a steady adherence to the law of armed conflict. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.3, footnote 52.
The US Naval Handbook (2007) states: “To be valid, a reprisal action must conform to the following criteria: 1. Reprisal must be ordered by an authorized representative of the belligerent government.” 
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, § 6.2.4.1.
The Handbook also states:
The President alone may authorize the taking of a reprisal action by U.S. forces. Although reprisals are lawful when the foregoing requirements are met, there is always the risk that such reprisals will trigger counter-reprisals by the enemy. The United States has historically been reluctant to resort to reprisal for just this reason. 
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, § 6.2.4.3.
The US Naval Handbook (1995) states: “To be valid, a reprisal action must conform to the following criteria: … 7. A reprisal action must cease as soon as the enemy is induced to desist from its unlawful activities and to comply with the law of armed conflict.” 
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), § 6.2.3.1.
The Annotated Supplement to the US Naval Handbook (1997), with reference to the rule that a reprisal must cease as soon as the enemy is induced to desist from its unlawful activities, states:
When, for example, one party to an armed conflict commits a breach of law but follows that violation with an expression of regret and promise that it will not be repeated, then any action taken by another party to “right” the situation cannot be justified as a lawful reprisal. 
United States, Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, prepared by the Oceans Law and Policy Department, Center for Naval Warfare Studies, Naval War College, Newport, Rhode Island, November 1997, § 6.2.3.1, footnote 44.
The US Naval Handbook (2007) states: “To be valid, a reprisal action must conform to the following criteria: … 7. A reprisal action must cease as soon as the enemy is induced to stop its unlawful activities and to comply with the law of armed conflict.” 
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, § 6.2.4.1.