Source: https://ihl-databases.icrc.org/customary-ihl/eng/docs/v2_cha_chapter5_rule21
Timestamp: 2019-04-21 23:29:17+00:00

Document:
Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), Geneva, 8 June 1977, Article 57(3). Article 57 was adopted by 90 votes in favour, none against and 4 abstentions. CDDH, Official Records, Vol. VI, CDDH/SR.42, 27 May 1977, p. 211.
When the military advantage to be gained leaves the choice open between several objectives, [the person responsible for ordering or launching an attack] is required to select the one, an attack on which involves least danger for the civilian population.
Draft Rules for the Limitation of the Dangers Incurred by the Civilian Population in Time of War, drafted by the International Committee of the Red Cross, September 1956, submitted to governments for their consideration on behalf of the 19th International Conference of the Red Cross, New Delhi, 28 October–7 November, Res. XIII, Article 8(a).
Objects and axes of attack should be chosen to minimise collateral damage wherever possible. Where a similar military advantage may be gained by attacking any one of several military objectives, the attack should be made against the objective which is likely to cause the least collateral damage. The same principle applies to choosing axes of advance or attack where more than one practicable and reasonable axis is available.
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 552; see also Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 957(f).
Objects and axes of attack should be chosen to minimise collateral damage wherever possible. Where a similar military advantage may be gained by attacking any one of several military objectives, the attack should be made against the objective that is likely to cause the least collateral damage. The same principle applies to choosing axes of advance or attack where more than one practicable and reasonable axis is available.
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 5.57.
Benin, Le Droit de la Guerre, III fascicules, Forces Armées du Bénin, Ministère de la Défense nationale, 1995, Fascicule III, p. 10.
Burundi, Règlement n° 98 sur le droit international humanitaire, Ministère de la Défense Nationale et des Anciens Combattants, Projet “Moralisation” (BDI/B-05), August 2007, Part I bis, p. 10; see also pp. 23, 33, 63, 64 and 81.
The proportionality test must be used in the selection of any target. Proportionality and multiple targets: Where a choice is possible between several legitimate targets for obtaining a similar military advantage, the target to be selected shall be the one on which an attack would be expected to cause the least civilian casualties and damage to civilian objects.
Canada, The Law of Armed Conflict at the Operational and Tactical Level, Office of the Judge Advocate General, 1999, p. 4-3, §§ 18 and 19; see also p. 7-5, § 49 (air to land operations).
1. Where a choice is possible between several legitimate targets for obtaining a similar military advantage, the target to be selected shall be the one on which an attack would be expected to cause the least civilian casualties and damage to civilian objects.
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 414.1.
When a choice is possible between several legitimate targets for obtaining a similar military advantage, the target to be selected shall be the one where the attack may be expected to cause the least danger to civilian lives and to civilian objects.
Canada, The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, § 716.5.
When a choice is possible between several legitimate military objectives for obtaining a similar military advantage, the objective to be selected shall be that the attack on which may be expected to cause the least danger to civilian lives and to civilian objects.
Côte d’Ivoire, Droit de la guerre, Manuel d’instruction, Livre IV: Instruction du chef de section et du commandant de compagnie, Manuel de l’élève , Ministère de la Défense, Forces Armées Nationales, November 2007, p. 28.
Croatia, Compendium “Law of Armed Conflicts”, Republic of Croatia, Ministry of Defence, 1991, p. 43; see also p. 41.
Croatia, Basic Rules of the Law of Armed Conflicts – Commanders’ Manual, Republic of Croatia, Ministry of Defence, 1992, § 50; see also § 66.
Before engaging an objective, every responsible military leader shall, when a choice is possible between several military objectives of equal importance, engage that objective the attack on which may be expected to cause the least incidental injury or damage.
Hungary, A Hadijog, Jegyzet a Katonai, Föiskolák Hallgatói Részére, Magyar Honvédség Szolnoki Repülötiszti Föiskola, 1992, p. 69; see also p. 66.
Italy, Regole elementari di diritto di guerra, SMD-G-012, Stato Maggiore della Difesa, I Reparto, Ufficio Addestramento e Regolamenti, Rome, 1991, § 50; see also § 66.
When a choice is possible between several military objectives for attaining a similar military advantage, the objective to be selected shall be that objective, the attack on which would cause the least danger to civilian persons and objects.
Madagascar, Le Droit des Conflits Armés, Ministère des Forces Armées, August 1994, Fiche No. 5-O, § 39.
Madagascar, Le Droit des Conflits Armés, Ministère des Forces Armées, August 1994, Fiche No. 6-O, § 21.
When a choice is possible between various military objectives, to attain equal military advantage, the objective chosen should be that where the attack can be expected to pose least danger to the lives of the civilian population and civilian objects.
Nigeria, International Humanitarian Law (IHL), Directorate of Legal Services, Nigerian Army, 1994, pp. 43–44, § 14.
Peru, Manual de Derecho Internacional Humanitario para las Fuerzas Armadas, Resolución Ministerial Nº 1394-2004-DE/CCFFAA/CDIH-FFAA, Lima, 1 December 2004, § 29.l.
Peru, Manual de Derecho Internacional Humanitario y Derechos Humanos para las Fuerzas Armadas, Resolución Ministerial No. 049-2010/DE/VPD, Lima, 21 May 2010, § 30(l), p. 243.
Spain, Orientaciones. El Derecho de los Conflictos Armados, Publicación OR7-004, 2 Tomos, aprobado por el Estado Mayor del Ejército, División de Operaciones, 18 March 1996, Vol. I, § 4.4.b; see also §§ 2.3.b.(1), 10.8.e.(2) and 10.8.f.(1).
Spain’s LOAC Manual (2007) states that “when a choice is possible between several military objectives for obtaining a similar military advantage, the objective expected to cause the least danger to civilian lives and civilian objects must be chosen”.
Spain, Orientaciones. El Derecho de los Conflictos Armados, Tomo 1, Publicación OR7–004, (Edición Segunda), Mando de Adiestramiento y Doctrina, Dirección de Doctrina, Orgánica y Materiales, 2 November 2007, § 4.4.b; see also §§ 2.3.b.(1) and 4.3.
In certain circumstances it is possible to reduce the risk to the civilian population and to civilian property if the military commander selects a different objective, from which he can achieve about the same military advantage as from the prime objective. In many situations, however, it is impossible to denote an alternative objective, for which reason the rule concerning second-line objectives has been given the reservation mentioned by way of introduction: “when a choice is possible”.
Togo, Le Droit de la Guerre, III fascicules, Etat-major Général des Forces Armées Togolaises, Ministère de la Défense nationale, 1996, Fascicule III, p. 10.
Ukraine, Manual on the Application of IHL Rules, Ministry of Defence, 11 September 2004, § 2.4.2.
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.32.
The Socialist Federal Republic of Yugoslavia’s Military Manual (1988) provides that if there is a choice between several military objectives for obtaining the same military advantage, military commanders must select the one which represents the least potential risk for the civilian population, “provided this does not particularly increase the danger to members of the armed forces undertaking the attack”.
Yugoslavia, Socialist Federal Republic of, Propisi o Primeri Pravila Medjunarodnog Ratnog Prava u Oruzanim Snagama SFRJ, PrU-2, Savezni Sekretarijat za Narodnu Odbranu (Pravna Uprava), 1988, § 72(3).
Under Ireland’s Geneva Conventions Act (1962), as amended in 1998, any “minor breach” of the 1977 Additional Protocol I, including violations of Article 57(3), is a punishable offence.
The precautionary principle is the cornerstone of a number of specific rules which are all considered to have attained customary status and to be applicable in internal armed conflicts … Among these rules is … the obligation to select the objective of an attack which may be expected to cause the least danger to civilian lives and to civilian objects when a choice is possible between several military objectives for obtaining a similar military advantage.
In 2010, in the Couso case, which concerned the killing of a Spanish journalist in Baghdad on 8 April 2003 by troops of the United States of America, the Criminal Chamber of Spain’s Supreme Court referred to norms of IHL relevant to the case under review, including Article 57(3) of the 1977 Additional Protocol I.
The Report on the Practice of Jordan notes that a booklet on the law of armed conflict prepared by the ICRC is used by military commanders. The booklet refers to the obligation to choose a target in the light of the obligation to minimize damage to civilians or civilian objects.
According to the Report on the Practice of Malaysia, the obligation to select, if a choice is available, the target representing the least potential risk for the civilian population forms part of Malaysian practice.
The Report on the Practice of Zimbabwe states that the provisions of Article 57 of the 1977 Additional Protocol I would be regarded as customary by Zimbabwe because of its adoption of the Geneva Conventions Amendment Act, which incorporates the 1977 Additional Protocol I into Zimbabwe’s law and practice.
When a choice is possible between several military objectives for obtaining a similar military advantage, the objective to be selected shall be that the attack on which would cause the least danger to civilian persons and objects.
To reduce civilian casualties and damage, equivalent alternative objectives and targets shall be selected whenever the mission given permits.
Frédéric de Mulinen, Handbook on the Law of War for Armed Forces, ICRC, Geneva, 1987, §§ 429 and 456.
In an appeal issued in October 1973, the ICRC urged all the belligerents in the conflict in the Middle East (Egypt, Iraq, Israel and the Syrian Arab Republic) to observe forthwith, in particular, the provisions of, inter alia, Article 50(3) of the draft Additional Protocol I, which stated: “When a choice is possible between several objectives, for obtaining a similar military advantage, the objective to be selected shall be that which will occasion the least danger to civilian lives and to civilian objects.” All the governments concerned replied favourably.

References: § 552
 § 957
 § 5
 § 49
 § 414
 § 716
 § 50
 § 66
 § 50
 § 66
 § 39
 § 21
 § 14
 § 29
 § 30
 § 4
 § 4
 § 2
 § 5
 § 72