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The Principle of Proportionality: ‘Force Protection’ as a Military Advantage

  • Robin Geiss (a1)

‘Force protection’ is a primary concern of every military commander. Undoubtedly, it is an important and legitimate factor in the planning of every attack. However, when it comes to the humanitarian proportionality principle there is considerable controversy over the question to what extent ‘force protection’ can be factored into the humanitarian proportionality calculus as a relevant military advantage to be weighed against expected civilian casualties, injuries and damage. This question is pursued in this article.

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1 Beard Jack M, ‘Law and War in the Virtual Era’ (2009) 103 American Journal of International Law 409, 420, 428–42, 444.

2 Ronald C Arkin, ‘Governing Lethal Behavior: Embedding Ethics in a Hybrid Deliberative/Reactive Robot Architecture’, GVU Technical Report GIT-GVU-07-11 (GVU Center, Georgia Institute of Technology, 2007), available at

3 Geiss Robin, ‘Asymmetric Conflict Structures’ (2006) 864 International Review of the Red Cross 757; Schmitt Michael N, ‘Asymmetrical Warfare and International Humanitarian Law’ in von Heinegg Wolff Heintschel and Epping Volker (eds), International Humanitarian Law Facing New Challenges (Springer 2007) 11.

4 See, for example, Benvenisti Eyal, ‘Human Dignity in Combat: The Duty to Spare Enemy Civilians’ (2006) 39 Israel Law Review 81, 81, 82, 90.

5 Article 57(3) of Protocol Additional to the Geneva Conventions of 12 August 1949 and relating to the Protection of Victims of International Armed Conflicts (entered into force 7 December 1978) 1125 UNTS 3 (‘Additional Protocol I’) provides that ‘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 may be expected to cause the least danger to civilian lives and to civilian objects’ (emphasis added).

6 The debate regarding art 57(2)(a)(ii) of Additional Protocol I is mainly focused on the question whether the wording ‘feasible’ encompasses also military considerations. Such a reading is supported, for example, by the declaration made by the UK at the time of ratification (28 January 1998). The text of the declaration is available at See also Protocol on Prohibitions or Restrictions on the Use of Mines, Booby-Traps and Other Devices (CCW Protocol II) (entered into force 2 December 1983) 1342 UNTS 137, art 3(4); Protocol on Prohibitions or Restrictions on the Use of Incendiary Weapons (CCW Protocol III) (entered into force 2 December 1983) 1342 UNTS 137, art 1(5); and Protocol on Prohibitions or Restrictions on the Use of Mines, Booby-Traps and Other Devices as amended on 3 May 1996 (‘Amended CCW Protocol II’) (entered into force 3 December 1998) 2048 UNTS 93, art 3(10), which define feasible precautions as ‘those precautions which are practicable or practically possible taking into account all circumstances ruling at the time, including humanitarian and military considerations’ (emphasis added). This is also the understanding adopted in the ICRC's Interpretive Guidance: see Melzer Nils, Interpretive Guidance on the Notion of Direct Participation in Hostilities (ICRC 2009) 75.

7 Benvenisti (n 4) 81–109; Walzer Michael, Just and Unjust Wars: A Moral Argument with Historical Illustrations (Basic Books 1977) 151.

8 US Counterinsurgency Field Manual, FM 3–24 MCWP 3-33.5 (Headquarters Department of the Army, December 2006) 162, note 7-30, available at See also Rogers Anthony PV, ‘Conduct of Combat and Risks Run by the Civilian Population’ (1982) 21 Military Law & Law of War Review 293, 310.

9 British Defence Doctrine (JWP 0-01) issued by the British Minister of Defence, 1996, cited in Rogers Anthony PV, ‘Zero-casualty Warfare’ (2000) 82 International Review of the Red Cross 165, 178 (note 41).

10 For Kasher and Yadlin ‘[J]eopardizing combatants rather than bystanders during a military act against a terrorist would mean shouldering responsibility for the mixed nature of the vicinity for no reason at all’: Kasher Asa and Yadlin Amos, ‘Military Ethics of Fighting Terror: An Israeli Perspective’ (2005) 4 Journal of Military Ethics 3, 18.

11 Dinstein Yoram, The Conduct of Hostilities under the Law of International Armed Conflict (CUP 2010) 141 (emphasis added).

12 Schmitt Michael N, ‘Precision Attack and International Humanitarian Law’ (2005) 87 International Review of the Red Cross 455, 462. According to Schmitt, the ‘survival of the military personnel and equipment is an appropriate consideration when assessing the military advantage of an attack in the proportionality context’; ibid.

13 Henderson Ian, The Contemporary Law of Targeting: Military Objectives, Proportionality and Precautions in Attack under Additional Protocol I (Martinus Nijhoff 2009) 62, 205.

14 ibid; Stephens Dale and Lewis Michael W, ‘The Law of Armed Conflict – A Contemporary Critique’ (2005) 6 Melbourne Journal of International Law 55, 72.

15 Solis Gary D, The Law of Armed Conflict: International Humanitarian Law in War (CUP 2010) 283, 285. See also Bring Ove, ‘International Humanitarian Law after Kosovo: Is Lex Lata Sufficient?’ (2002) 71 Nordic Journal of International Law 39, 47.

16 Oeter Stefan, ‘Collateral Damages – Military Necessity and the Right to Life’ in Tomuschat Christian, Lagrange Evelyne and Oeter Stefan (eds), The Right to Life (Martinus Nijhoff 2010) 167, 167, 185.

17 Fenrick William J, ‘Attacking the Enemy Civilian as a Punishable Offense’ (1997) 7 Duke Journal of Comparative and International Law 539, 548–49.

18 Stefan Oeter, ‘Is the Principle of Distinction Outdated?’ in Wolff Heintschel von Heinegg and Volker Epping (n 3) 58. Oeter goes on to argue that ‘[the] more technological possibilities you have as a belligerent to avoid direct risk exposure of your own military personnel to enemy force, the more collateral damage you will tend to find justified and proportionate if it helps to spare the lives of your own soldiers’.

19 Solis (n 15) 285. According to Sandoz ‘If the price to absolute security of one's own soldiers is heavy casualties among civilians, this price is too high’: Sandoz Yves, ‘Commentary’ in Wall Andru E (ed), Legal and Ethical Lessons of NATO's Kosovo Campaign, International Law Studies, vol 78 (Naval War College, Newport RI 2002) 273, 277.

20 Report of the Expert Meeting, ‘Targeting Military Objectives’ (University Centre for International Humanitarian Law 2005) 17, available at (emphasis added).

21 See Final Report to the Prosecutor by the Committee established to review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia (2000) 39 International Legal Materials 1257, 1273. According to the report ‘[t]he questions which remain unresolved once one decides to apply the principle of proportionality include the following: a) What are the relative values to be assigned to the military advantage gained and the injury to non-combatants and or the damage to civilian objects? b) What do you include or exclude in totaling your sums? c) What is the standard of measurement in time or space?, and d) To what extent is a military commander obligated to expose his own forces to danger in order to limit civilian casualties or damage to civilian objects?’.

22 Official Records of the Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts, Geneva (1974–1977), vol XV (Federal Political Dept 1978) CDDH/III/224, at 331 (emphasis added; brackets appeared already in the Working Group's original text).

23 Official Records of the Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law Applicable in Armed Conflicts, Geneva (1974–1977), vol XIV (Federal Political Dept 1978) CDDH/III/SR.24, at 220 (Mr Aldrich, USA).

24 ibid (emphasis added).

25 As far as objects are concerned, the presumption of civilian character in case of doubt is also contained in Amended Protocol II to the Convention on Certain Conventional Weapons, art 3(8)(a). The ICRC's Interpretive Guidance on the Notion of Direct Participation in Hostilities (n 6) 74, provides that ‘[i]n case of doubt, the person must be presumed to be protected against direct attack’. For a critique of the distribution of risks inherent in this approach see Schmitt Michael N, ‘Deconstructing Direct Participation in Hostilities: The Constitutive Elements’ (2010) 42 NYU Journal of International Law and Politics 697, 737, 738. Schmitt suggests that there should be ‘a presumption that questionable activities qualify as acts of direct participation’ and that ‘[g]ray areas should be interpreted liberally, i.e., in favor of finding direct participation’, n 123 citing Schmitt Michael N, ‘Direct Participation in Hostilities and 21st Century Armed Conflict’ in Fischer Horst and others (eds), Crisis Management and Humanitarian Protection: Festschrift für Dieter Fleck (Berliner Wissenschafts-Verlag 2004) 509.

26 With regard to military objects the ICRC Study of Customary International Humanitarian law (‘ICRC Study’) concludes that ‘the issue of how to classify an object in case of doubt is not entirely clear’: see Henckaerts Jean-Marie and Doswald-Beck Louise, Customary International Humanitarian Law, Vol I: Rules (ICRC, CUP 2005) 35, Rule 10. See also US Department of Defense, Final Report to Congress on the Conduct of the Persian Gulf War, Appendix O, The role of the law of war (1992) 31 International Legal Materials 612–44, 627. According to the Report, ‘[t]his language, which is not a codification of the customary practice of nations, causes several things to occur that are contrary to the traditional law of war. It shifts the burden for determining the precise use of an object from the party controlling that object (and therefore in possession of the facts as to its use) to the party lacking such control and facts, i.e. from defender to attacker. This imbalance ignores the realities of war in demanding a degree of certainty of an attacker that seldom exists in combat. It also encourages a defender to ignore its obligation to separate the civilian population, individual civilians and civilian objects from military objectives, as the Government of Iraq illustrated during the Persian Gulf War’ (emphasis added).

27 See declarations and reservations made by France and the UK upon ratification of Additional Protocol I, available at Against this background the ICRC Study (n 26) concludes ‘… that, in case of doubt, a careful assessment has to be made under the conditions and restraints governing a particular situation as to whether there are sufficient indications to warrant an attack’. The ICRC Study also points out that ‘[i]n the case of non-international armed conflicts, the issue of doubt has hardly been addressed in State practice,…’ (n 26) 36, 24.

28 Benvenisti (n 4) 93.

29 See, for example, Program on Humanitarian Policy and Conflict Research at Harvard University (HPCR), Commentary on the HPCR Manual on International Law Applicable to Air and Missile Warfare (The President and Fellows of Harvard College 2010) 44–5, available at

30 Dinstein (n 11) 95.

31 ibid.

32 Commentary on the HPCR Manual on International Law (n 29) 45.

33 US Department of Defense, ‘Conduct of the Persian Gulf War: Final Report to Congress’ (April 1992) 699, available at

34 Commentary on the HPCR Manual on International Law (n 29) 45. With regard to the more restrictive approach that is reflected in the ICRC Commentary the HPCR commentary states: ‘A better approach is to understand military advantage as any consequence of an attack which directly enhances friendly military operations or hinders those of the enemy. This could, for example, be an attack that reduces the mobility of the enemy forces without actually weakening them, such as the blocking of an important line of communication.’

35 Dinstein (n 11) 93. Of course, the question where to draw the line between relevant military advantages and irrelevant political advantages has at times been controversially discussed. A certain degree of ultimately unavoidable peripheral vagueness has always remained. After all, military ends are never entirely autonomous in themselves and war itself ultimately remains a political act: see Carnahan Burrus M, ‘Lincoln, Lieber and the Laws of War: The Origins and Limits of the Principle of Military Necessity’ (1998) 92 American Journal of International Law 213, 213, 231; Geiss Robin, ‘Military Necessity: A Fundamental “Principle” Fallen into Oblivion’ in Fabri Helen Ruiz, Wolfrum Rüdiger and Gogolin Jana (eds), Select Proceedings of the European Society of International Law (Hart 2008) 554, 557.

36 Commentary on the HPCR Manual on International Law (n 29) 45.

37 According to the US Counterinsurgency Field Manual: ‘In conventional operations, proportionality is usually calculated in simple utilitarian terms: civilian lives and property lost versus enemy destroyed and military advantage gained’ (n 8) n 7–32 (emphasis added).

38 The US Counterinsurgency Field Manual (n 8) 162, note 7–30, for example, refers only to the ‘concrete and direct military advantage expected to be gained’. Similarly, Israel's manual on the law of war refers to ‘harm on the civilian population that is disproportionate to the expected military gain’: Israel, Law of War in the Battlefield, Manual (Advocate General Headquarters, Military School 1998) 40 (emphasis added). In her dissenting opinion in the Nuclear Weapons case before the ICJ in 1996, Judge Higgins stated: ‘Even a legitimate military target may not be attacked if the collateral civilian casualties would be disproportionate to the specific military gain from the attack’: Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion of 8 July 1996 [1996] ICJ Rep 226, Dissenting Opinion of Judge Higgins [20] (emphasis added).

39 Australia, upon ratification, declared: ‘In relation to paragraph 5(b) of Article 51 and to paragraph 2(a)(iii) of Article 57, it is the understanding of Australia that references to the “military advantage” are intended to mean the advantage anticipated from the military attack considered as a whole and not only from isolated or particular parts of that attack and that the term “military advantage” involves a variety of considerations including the security of attacking forces. It is further the understanding of Australia that the term “concrete and direct military advantage anticipated” used in Articles 51 and 57, means a bona fide expectation that the attack will make a relevant and proportional contribution to the objective of the military attack involved.’ The declaration is available at

40 The Commander's Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7 (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), para 8.1.1 (emphasis added).

41 See Solis (n 15) (emphasis added).

42 Blum Gabriella, ‘The Dispensable Lives of Soldiers’ (2010) 2 Journal of Legal Analysis 69, 78, available at

43 The term is borrowed from Kasher and Yadlin (n 10). For a critique of their approach, however, see Section 4.2.1.

44 See, for example, The Commander's Handbook (n 40) which states that the term military advantage ‘refers to the advantage anticipated from the military operation of which the attack is a part, taken as a whole, and not from isolated or particular parts of that operation’, para

45 See nn 39 and 40.

46 The Rules concerning the Control of Wireless Telegraphy in Times of War and Air Warfare (The Hague, February 1923), art 24(1) stipulates: ‘An air bombardment is legitimate only when it is directed against a military objective, i.e. an objective whereof the total or partial destruction would constitute an obvious military advantage for the belligerent’ (emphasis added). The rules are available at

47 Institut de Droit International, Resolution entitled ‘The Distinction between Military Objectives and Non-Military Objectives in General and Particularly the Problems Associated with Weapons of Mass Destruction’ in Résolutions de l'Institut de Droit International 1957–1991 (Edition Pedone 1992) 67, 69 art 2, cited in Dinstein (n 11) 93.

48 Sandoz Yves, Swinarski Christophe and Zimmermann Bruno (eds), Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 (ICRC/Martinus Nijhoff 1987) 677, 684.

49 Dinstein (n 11) 134.

50 ibid.

51 Dörmann Knut, Elements of War Crimes under the Rome Statute of the International Criminal Court: Sources and Commentary (CUP 2003) 161, n 36.2.

52 In 1999 the ICRC submitted a paper to the Working Group on Elements of Crimes of the Preparatory Commission for the ICC, emphasising that ‘[t]he addition of the words “clearly” and “overall” in the definition of collateral damage [in Article 8(2)(b)(iv) of the 1998 ICC Statute] is not reflected in any existing legal source. Therefore, the addition must be understood as not changing existing law’: see ICRC, Paper relating to the Crimes listed in Article 8, paras 2(b)(i), (ii), (iii), (iv), (v), (vi), (ix), (xi), (xii) of the Statute of the ICC annexed to UN Doc PCNICC/1999/WGEC/INF.2/Add.1, 30 July 1999, 29.

53 See Aldrich George H, ‘Prospects for United States Ratification of Additional Protocol I to the 1949 Geneva Conventions’ (1991) 85 American Journal of International Law 1. Despite the refusal to ratify Additional Protocol I, the US claims to adhere to Article 57 as a matter of customary law: see Fenrick William J, ‘The Rule of Proportionality and Protocol I in Conventional Warfare’ (1982) 98 Military Law Review 91; Taft William H IV, ‘The Law of Armed Conflict after 9/11: Some Salient Features’ (2003) 28 Yale Journal of International Law 319, 322.

54 The text of this and of the other parallel declarations are available at Moreover, the ICC Statute, art 8(2)(b), criminalises such attacks only when committed in the knowledge ‘that such attack will cause incidental loss of life or injury to civilians or damage to civilian objects or widespread, long-term and severe damage to the natural environment which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated’ (emphasis added). See also ICRC Study (n 26) 50.

55 Zimmermann Andreas, ‘The Second Lebanon War: Jus ad Bellum, Jus in Bello and the Issue of Proportionality’ (2007) 11 Max Planck Yearbook of United Nations Law 99, 99, 132.

56 Dinstein (n 11) 94, citing Oeter Stefan, ‘Methods and Means of Combat’, in Fleck Dieter (ed), The Handbook of International Humanitarian Law (OUP 2008) 186.

57 Dinstein (n 11) 93.

58 ibid, 95.

59 Even ‘an attack as a whole’ is a finite event. In this context, Dinstein criticises, as a gross exaggeration, the finding of the Eritrea-Ethiopia Claims Commission which held that ‘a definite military advantage must be considered in the context of its relation to the armed conflict as a whole at the time of the attack’ and ‘not simply in the context of a specific attack’: see Eritrea-Ethiopia Claims Commission: Partial Award – Western Front, Aerial Bombardment and Related Claims, Eritrea's Claims 1, 3, 5, 9–13, 14, 21, 25, 26 (2005), (2006) 45 International Legal Materials 396, 418. According to Dinstein, ‘the admissible mise-en-scène is only “an attack as a whole” and not “the armed conflict as a whole”’ (n 11) 95.

60 But see the interpretation by Kasher and Yadlin of the accumulative benefits doctrine in relation to the fight against terrorists, Section 4.2.1.

61 Sandoz and others (n 48).

62 Michael Walzer, ‘Justice and Injustice in the Gulf War’ in David E Decosse (ed) But Was it Just? – Reflections on the Morality of the Persian Gulf War (Bantam Doubleday Dell Publishing Group 1991) 7.

63 This may seem odd given that IHL, unlike the law enforcement paradigm, is not threat-dependent. A military objective may be attacked at any time irrespective of whether it poses an imminent threat to one's own forces or not. However, where the justification of civilian casualties and damage is at issue, the threat posed by the enemy starts to matter because it may have an influence on the relative value of the military advantage that is to be gained from an attack. This is a logical consequence of regarding ‘force protection’ as a relevant military advantage. Destroying an enemy tank that currently attacks will be perceived as a more important military advantage than the destruction of the same tank while it is just driving through a village. In the former scenario the military advantage gained consists of the destruction of the enemy tank plus the protection of the forces that were attacked by that tank, whereas in the latter scenario the military advantage gained consists only of the destruction of the enemy's tank.

64 See Sassòli Marco, ‘Ius Ad Bellum and Ius in Bello – The Separation between the Legality of the Use of Force and Humanitarian Rules to be respected in Warfare: Crucial or Outdated?’ in Schmitt Michael N and Pejic Jelena (eds), International Law and Armed Conflict: Exploring the Faultlines, Essays in Honour of Yoram Dinstein (Martinus Nijhoff 2007) 241–64, 246–54; Gardam Judith G, ‘Proportionality and Use of Force in International Law’ (1993) 87 American Journal of International Law 391, 410.

65 Kasher and Yadlin (n 10) 14, 15.

66 ibid, 20.

67 Of course, Kasher and Yadlin's argument is specifically designed to apply to the fight against terrorism. However, it is unclear how they would apply a different reasoning in the context of a ‘regular’ armed conflict. State duties vis-à-vis their own citizens remain the same.

68 Similarly, the US Counterinsurgency Field Manual (n 8) 162, note 7–32, provides: ‘In COIN environments, the number of civilian lives lost and property destroyed needs to be measured against how much harm the targeted insurgent could do if allowed to escape’ (emphasis added).

69 See Oeter (n 16); Fenrick (n 17).

70 According to Benvenisti, ‘[w]hen armies attack they face two conflicting obligations. The first is the obligation to ensure the rights of their own nationals, and the second is the obligation to respect enemy nationals by not targeting them and by striving to reduce the harms the army inflict on them’: Benvenisti (n 4) 89.

71 See Section 4.2.

72 ibid.

73 Criteria such as the size, importance or strategic location of the protected forces may be taken into consideration in order to determine their military value. All other things being equal, protecting only five soldiers is evidently of a lower relative value than the protection of 500 soldiers. As Ian Henderson has stated: ‘Crudely, certain elements of a military are more valuable to it in terms of their military capabilities and replaceability than other parts’: Henderson (n 13) 205. See also Greenwood Christopher, ‘The Twilight of the Law of Belligerent Reprisals’ (1989) 20 Netherlands Yearbook of International Law 35, 45.

74 Schmitt (n 12) 462.

75 Given that proportionality is necessarily assessed ex ante, the military and humanitarian effects of the attack are always to some degree speculative and ultimately depend on subjective risk assessments: see Amichai Cohen and Yuval Shany, ‘A Development of Modest Proportions: The Application of the Principle of Proportionality in the Israeli Supreme Court Judgment on the Lawfulness of Targeted Killings’ (Research Paper No 5–07, April 2007), available at But the uncertainty that inherently lies in every ex ante decision is different from the speculation that derives from comparing a future attack (and its anticipated consequences) with a hypothetical attack. In the latter case the uncertainty is not about what is most likely to happen if an envisaged attack is carried out, but what would have happened if a hypothetical attack – that exists only in the strategic thinking of military commanders – had been executed.

76 The little clarity that exists derives primarily from the limiting adjectives ‘concrete’ and ‘direct’ rather than the ‘military advantage’ notion itself.

77 A genuine balancing judgment is possible only if there is at least a theoretical possibility to fill both scale pans with the same amount of things. Thus, if the military advantage notion is interpreted broadly, as a logical consequence a similarly broad approach should be employed with regard to civilian casualties and damage. Otherwise the proportionality assessment is distorted from the outset. This is supported by the wording of arts 51(5)(b) and 57(2)(a)(iii) of Additional Protocol I. Whereas the military advantage is limited by the adjectives ‘concrete and direct’, no such limiting qualifiers apply with respect to civilian damage. The word ‘incidental’ is certainly broader than the requirements of being ‘concrete and direct’. Therefore, at least foreseeable long-term repercussions on the civilian population have to be taken into consideration when determining what civilian damage may be expected from an attack. See Geiss Robin, ‘The Conduct of Hostilities in Asymmetric Conflicts – Reciprocity, Distinction, Proportionality, Precautions’ (2010) 23 Journal of International Law of Peace and Armed Conflicts 122, 130.

Warm thanks are due to Cordula Droege, Nils Melzer, Yaël Ronen, Henning Lahmann and the anonymous reviewers for their critique and helpful comments.

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