1 Convention for the Amelioration of the Condition of the Wounded in Armies in the Field, Geneva, 22 August 1864. In this note, the terms ‘wounded and sick’ are used as defined in Art. 8(a) of the Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of International Armed Conflicts, 8 June 1977, 1125 UNTS 3 (entered into force 7 December 1978) (hereinafter AP I). This definition is also relevant for non-international armed conflicts: see Sandoz, Yves, Swinarski, Christophe and Zimmermann, Bruno (eds.), Commentary on the Additional Protocols, ICRC, Geneva, 1987Google Scholar (hereinafter ICRC Commentary), para. 4637.

2 Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field of 12 August 1949, 75 UNTS 31 (entered into force 21 October 1950) (hereinafter GC I); Geneva Convention for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea of 12 August 1949, 75 UNTS 85 (entered into force 21 October 1950) (hereinafter GC II); Arts. 8ff of AP I; Arts. 7ff of the Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts, 8 June 1977, 1125 UNTS 609 (entered into force 7 December 1978) (hereafter AP II); ICRC, Customary International Humanitarian Law, Vol. I: Rules, Jean-Marie Henckaerts and Louise Doswald-Beck (eds), Cambridge University Press, Cambridge, 2005 (hereinafter ICRC Customary Law Study), Rules 25–30 and 109–111.

3 Arts. 41 and 48 in fine of AP I; Rule 1, second sentence, of the ICRC Customary Law Study, above note 2.

4 Solis, Gary D., The Law of Armed Conflict: International Humanitarian Law in War, Cambridge University Press, Cambridge, 2010, p. 191CrossRefGoogle Scholar.

5 Henderson, Ian, The Contemporary Law of Targeting: Military Objectives, Proportionality and Precautions in Attack under Additional Protocol I, Martinus Nijhoff Publishers, Leiden, 2009, pp. 195–196CrossRefGoogle Scholar (for medical units) and p. 206 (for medical personnel).

6 Bartels, Rogier, ‘Dealing with the principle of proportionality in armed conflict in retrospect: the application of the principle in international criminal trials’, in Israel Law Review, Vol. 46, No. 2, July 2013CrossRefGoogle Scholar, p. 304. While Bartels argues on the basis of Art. 50 of AP I that persons hors de combat other than civilians, such as wounded soldiers, do not benefit from the protection of the principle of proportionality under AP I or the Rome Statute, he is not entirely clear on whether he considers that this protection exists under customary IHL; he indeed asserts that ‘[i]t is submitted here that the principle of proportionality is broader than the rules that codified the principle in Additional Protocol I. The principle underlying Articles 52 and 57 of Additional Protocol I would include prohibited attacks on military objects that would cause excessive damage to any person who cannot be targeted directly under IHL; not only civilians but also persons hors de combat’ (p. 304). Bartels' arguments with regard to Art. 8(2)(b)(iv) of the Rome Statute are outside of the scope of this opinion note.

7 ‘In the ICRC's view, any assessment of the expected incidental harm under the rule of proportionality must take into account possible deaths or injuries among all the medical personnel, including military medical personnel, as well as combatants who are hors de combat. This stems from the central obligation to respect and protect these persons': 14th Bruges colloquium, 17 and 18 October 2013, keynote address by Ms. Christine Beerli, ICRC vice-president, available at: www.icrc.org/eng/resources/documents/statement/2013/10-18-protected-person-bruges.htm (last visited 3 April 2014). See also the article by Alexander Breitegger in this issue of the Review.

8 For medical persons and objects, see Art. 21 of GC I, Art. 13 of AP I, Art. 11 of AP II, and Rules 25, 28 and 29 of the ICRC Customary Law Study, above note 2. For the wounded and sick, see the definition under Art. 8(a) of AP I.

9 Art. 51(4) of AP I; Rule 14 of the ICRC Customary Law Study, above note 2.

10 Art. 57 of AP I; Rules 15–21 of the ICRC Customary Law Study, above note 2.

11 Art. 58 of AP I; Rules 22–24 of the ICRC Customary Law Study, above note 2.

12 ‘Article 57 – Precautions in attack

[…]

1. 2.

   2. With respect to attacks, the following precautions shall be taken:

   1. (a)

      (a) those who plan or decide upon an attack shall:

      1. (i)

         (i) do everything feasible to verify that the objectives to be attacked are neither civilians nor civilian objects and are not subject to special protection but are military objectives within the meaning of paragraph 2 of Article 52 and that it is not prohibited by the provisions of this Protocol to attack them;

         […]

   2. (b)

      (b) an attack shall be cancelled or suspended if it becomes apparent that the objective is not a military one or is subject to special protection’ (emphasis added).

13 Arts. 57(1) and 57(5) of AP I speak of ‘the civilian population, civilians and civilian objects’; Art. 57(2)(a)(ii) of ‘loss of civilian life, injury to civilians and damage to civilian objects’; Art. 57(2)(c) of ‘the civilian population’; Arts. 57(3) and 57(4) of ‘civilian lives and civilian objects’; and Art. 58 of ‘the civilian population, individual civilians and civilian objects’.

14 Arts. 51(5)(b), 57(2)(a)(iii), and (57)(2)(b), second sentence, of AP I all speak of ‘loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof’.

15 Report of the Secretary-General Pursuant to Paragraph 2 of Security Council Resolution 808 (1993), S/25704, 3 May 1993, para. 41. International Criminal Tribunal for the former Yugoslavia (ICTY), The Prosecutor v. Duško Tadić, Case No. IT-94-1, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, 2 October 1995, para. 87.

16 Convention (IV) respecting the Laws and Customs of War on Land and its annex: Regulations concerning the Laws and Customs of War on Land, The Hague, 18 October 1907 (entered into force 26 January 1910), Regulations, Art. 27(1). The same provision is found in the 1923 Hague Rules on Air Warfare, Art. XXV; see ‘General Report of the Commission of Jurists at the Hague’, in The American Journal of International Law, Vol. 17, No. 4, Supplement: Official Documents, October 1923, pp. 242–260.

17 Art. 52(2) of AP I; Rule 8 of the ICRC Customary Law Study, above note 2.

18 Doermann, Knut, ‘Obligations of international humanitarian law’, in Military and Strategic Affairs, Vol. 4, No. 2, September 2012, pp. 11–23Google Scholar, p. 15; Bothe, Michael, Partsch, Karl Josef and Solf, Waldermar A., New Rules for Victims of Armed Conflicts, Martinus Nijhoff Publishers, The Hague, 1982, p. 326Google Scholar; Sassòli, Marco and Cameron, Lindsey, ‘The protection of civilian objects: current state of the law and issues de lege ferenda’, in Ronzitti, Natalino and Venturini, Gabriella (eds), The Law of Air Warfare: Contemporary Issues, Eleven International, The Hague, 2006, pp. 35–74Google Scholar, p. 48.

19 ‘To be used, outside of their humanitarian function, to commit acts harmful to the enemy’, is the standard leading to the loss of the special protection afforded to medical objects because of their function (subject to other safeguards such as the obligation to issue a warning); cf. Art. 21 of GC I and Art. 13 of AP I; Rules 28–29 of the ICRC Customary Law Study, above note 2.

20 Henderson, above note 5, p. 195. Henderson also develops a somewhat circular reasoning according to which medical objects were granted special protection because they were military objectives in the first place, which proves they are not entitled to the general protection granted to civilian objects. This would arguably mean that civilian medical units – or any other specially protected object (or person) – should also be considered a military objective because otherwise they would not need the special protection. In the view of this author, this argument is therefore also not convincing.

21 Rule 9 of the ICRC Customary Law Study, above note 2.

22 Rule 22(a) of the Manual on International Law applicable to Air and Missile Warfare, HPCR, Bern, 2009 (hereafter HPCR Air and Missile Warfare Manual) specifically excludes medical transports from military vehicles when giving examples of military objectives by nature. Dinstein gives the same argument with regard to POW camps: see Dinstein, Yoram, The Conduct of Hostilities under the Law of International Armed Conflict, 2^nd ed., Cambridge University Press, Cambridge, 2010CrossRefGoogle Scholar, para. 305.

23 The ICRC Commentary on the 1973 Draft Additional Protocols makes it clear when talking about paragraphs that included notably the draft proportionality rules (draft Arts. 50(1)(a) and (b), which became Arts. 57(2)(a)(i) and (iii) and 57(2)(b) of AP I): ‘All these various factors with their probable or possible effects on protected civilians and civilian objects must therefore be borne in mind when planning, deciding (sub-paragraph (a)) and launching (sub-paragraph (b)) the attack’. A footnote attached to the words ‘civilian objects’ clarifies: ‘Not only within the meaning of Art. 47 (2) [which listed ‘objects designed for civilian use … and all objects which are not military objectives’], but any object protected under existing treaty law or customary international law (civilian and military hospitals, cultural objects, hospital and safety zones, etc.).’ ICRC, Draft Additional Protocols to the Geneva Conventions of August 12, 1949, Commentary, Geneva, 1973, p. 65Google Scholar, fn. 32 (emphasis added).

24 Rule 5 of the ICRC Customary Law Study, above note 2. Participants in a levee en masse are also not civilians: see Art. 4(A)(6) of the Geneva Convention relative to the Treatment of Prisoners of War of 12 August 1949, 75 UNTS 135 (entered into force 21 October 1950).

25 For the concept of civilian in non-international armed conflict, see ICRC, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law, 2009, pp. 27ff.

26 I. Henderson, above note 5, p. 206; R. Bartels, above note 6, p. 304.

27 For example, the special protection afforded to medical personnel, transports, and units, whether military or civilian, will cease only after due warning has been given (Art. 21 of GC I, Art. 19 of the Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field of 12 August 1949, 75 UNTS 287 (entered into force 21 October 1950) (hereafter GC IV), Art. 13 of AP I, and Art. 11 of AP II), whereas no warning is required before directing an attack against a civilian (other than civilians entitled to special protection such as civilian medical personnel) who takes a direct part in hostilities.

28 See Art. 19(1) of GC I, Art. 12(1) of AP I, and Art. 11(1) of AP II for medical units, and Art. 41 of AP I for persons hors de combat. The rules on the protection of the medical mission neither expressly prohibit direct attacks on civilian medical personnel (see Art. 20 of GC IV and Art. 9 of AP II), though they enjoy the protection of the general prohibition of directing attacks against civilians.

29 See Art. 48 of AP I, which opens Part IV of the First Additional Protocol, in which all three principles of distinction, proportionality, and precautions are developed.

30 For the wounded and sick, see Art. 12 of GC I, Art. 10 of AP I, and Art. 7 of AP II. For medical personnel, see Art. 24 of GC I, Art. 20 of GC IV, Art. 15 of AP I, and Art. 9 of AP II; Rule 27 of the ICRC Customary Law Study, above note 2. The ICRC Commentary on Art. 48 of AP I (above note 1, para. 1872) makes the link between the words used in Arts. 10 and 48 of AP I.

31 Pictet, Jean (ed.), Commentary on the Geneva Conventions of 12 August 1949, Vol. 1: Geneva Convention for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field, Geneva, 1952, pp. 134–135Google Scholar, on Art. 12 of GC I.

32 Ibid., p. 220, on Art. 12 of GC I. The ICRC Commentary on Art. 19 of GC I again refers to it with regard to military medical units: ibid., p. 196.

33 ICRC Commentary on Art. 10(1) of AP I (above note 1), para. 446: ‘“Respect” means “to spare, not to attack”, while “protect” means “to come to someone's defence, to lend help and support”. Thus it is prohibited to attack the wounded, sick or shipwrecked, to kill them, maltreat them or injure them in any way, and there is also an obligation to come to their rescue.’ The understanding of the terms ‘respect and protect’ as explained in the Commentaries to GC I and AP I could imply a stronger protection than the prohibition of excessive incidental ham, as they state that it is prohibited to harm, kill or injure them ‘in any way’. On the face of it, this could be said to prohibit any incidental harm to these specially protected persons.

34 Bugnion, François, The International Committee of the Red Cross and the Protection of War Victims, ICRC, Geneva, Macmillan, Oxford, 2003, pp. 471ffGoogle Scholar.

35 Pictet, Jean (ed.), Commentary on the Geneva Conventions of 12 August 1949, Vol. IV, Geneva Convention relative to the Protection of Civilian Persons in Time of War, ICRC, Geneva, 1958, pp. 147–148Google Scholar, on Art. 18. Here again, Henderson's argument that ‘nothing in the drafting history of article 19 of GC I … indicates that “respected and protected” extends so far as to mean that collateral damage to military medical units must be considered when determining the proportionality of an attack on a nearby military objective’ is unconvincing, even if it would have been made for persons rather than objects (I. Henderson, above note 5, p. 196). In 1949, the proportionality rule had not yet emerged in such clarity as it did in Art. 51 of AP I, so few conclusions can be drawn about it from the drafting history of the Geneva Conventions on proportionality specifically, but the drafting history makes clear that the obligation to respect and protect must be understood broadly.

36 Hays Parks, W., ‘Air war and the law of war’, in The Air Force Law Review, Vol. 32, No. 1, 1990, p. 57Google Scholar.

37 Such as Art. 10 of AP I and Art. 7 of AP II for wounded and sick, and Art. 24 of GC I and Art. 9 of AP II for medical personnel.

38 ICRC Commentary on Art. 12 of AP I (above note 1), para. 540 (emphasis added).

39 M. Bothe, K. J. Partsch and W. A. Solf, above note 18, p. 118f (emphasis added). The next paragraph confirms that this refers to the principle as stated in Arts. 51(5)(b) and 57(2)(a)(iii) of AP I: ‘In applying the proportionality test to the protection of medical units against collateral damage, everything depends on the concrete situation. The yardstick of proportionality is the concrete and direct military advantage anticipated’ (p. 119).

40 ICRC Commentary on Art. 10 of AP I (above note 1), para. 444. See in particular Arts. 8, 10(1), and 12(1) of AP I, as well as Art. 15 of AP I, which extends to civilians the protection already afforded to military medical personnel by Art. 24 of GC I. The Commentary's introduction on Part II of AP I states:

41 See Schmitt, Michael N., ‘Military necessity and humanity in international humanitarian law: preserving the delicate balance’, in Virginia Journal of International Law, Vol. 50, No. 4, 2010, pp. 795–839Google Scholar, p. 798. On the principle of proportionality as a specific expression of these two principles, see M. Bothe, K. J. Partsch and W. A. Solf, above note 18, p. 309; M. Sassòli and L. Cameron, above note 18, p. 63; Fenrick, W. J., ‘The rule of proportionality and Protocol I in conventional warfare’, in Military Law Review, Vol. 98, 1982, p. 125Google Scholar; United Kingdom, The Joint Service Manual of the Law of Armed Conflict, JSP 383, 2004, paras. 2.6.2 and 5.33.2.

42 Art. 43(2) of AP I. Wounded or sick combatants who directly participate in hostilities are excluded from the definition of wounded and sick under Art. 8(a) of AP I, which requires that they refrain from any act of hostility.

43 Though referring to the prohibition of direct attack against an enemy hors de combat under Art. 41 of AP I, the ICRC Commentary an AP I recalls that ‘[i]t is a fundamental principle of the law of war that those who do not participate in the hostilities shall not be attacked. In this respect harmless civilians and soldiers “hors de combat” are a priori on the same footing’ (above note 1, para. 1605, emphasis added).

44 M. Bothe, K. J. Partsch and W. A. Solf, above note 18, p. 221.

45 Ibid., p. 119

46 Doermann, Knut, Elements of War Crimes under the Rome Statute of the International Criminal Court, Cambridge University Press, Cambridge, 2002, p. 345Google Scholar.

47 ICRC Customary Law Study, above note 2 p. xxxviii. On state practice relevance, see Vienna Convention on the Law of Treaties, 23 May 1969, 1155 UNTS 331 (entered into force 27 January 1980), Art. 31(3)(b).

48 Australia: Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, does not limit its definition of collateral damage to civilians or civilian objects in its Glossary (though it does in para. 5.2). United States: Joint Targeting, Joint Publication 3-60 (3 January 2013) defines collateral damage as ‘[u]nintentional or incidental injury or damage to persons or objects that would not be lawful military targets in the circumstances ruling at the time’ (p. GL – 4 Terms and definitions), a definition which includes protected persons and objects other than civilians and civilian objects, and informs the entire publication when the term ‘collateral damage’ is used in an unqualified manner. JP 3-60 also emphasises that ‘[t]he United States of America places a high value on preserving civilian and noncombatant lives and property and seeks to accomplish its mission through the discriminate application of forces with minimal collateral damage’ (p. III – 1; all emphasis added). The definition of collateral damage given in JP 3-60 is included in the Department of Defense Dictionary of Military and Associated Terms, Joint Publication 1-02 (As Amended Through 15 March 2014). Though now rescinded, the US Air Force pamphlet Commander's Handbook on the Law of Armed Conflict, 1980, generally defined civilians as follows: ‘Civilians, in this pamphlet, are all persons other than those who are subject to direct attack under paragraphs 2–6 through 2–8’ (paras. 3-1); paras. 2–7 of the pamphlet excluded military medical personnel and the sick and wounded from those subject to direct attack. So for the pamphlet, through a definition more akin to Art. 52 than Art. 50 of AP I, military medical personnel and wounded and sick combatants directly fell under the definition of civilians despite the usual meaning of that term (see above for the discussion of Art. 52 of AP I).

49 Australia: Law of Armed Conflict, above note 48, includes non-combatants other than civilians when setting out the principle of proportionality (para. 2.8). Canada: The Law of Armed Conflict at the Operational and Tactical Levels, Office of the Judge Advocate General, 13 August 2001, para. 204.5: ‘In deciding whether the principle of proportionality is being respected, the standard of measurement is the anticipated contribution to the military purpose of an attack or operation considered as a whole. The anticipated military advantage must be balanced against other consequences of the action, such as the adverse effect upon civilians or civilian objects. It involves weighing the interests arising from the success of the operation on the one hand, against the possible harmful effects upon protected persons and objects on the other.’ New Zealand: Interim Law of Armed Conflict Manual, DM 112, New Zealand Defence Force, Headquarters, Directorate of Legal Services, Wellington, November 1992, para. 207: ‘The principle of proportionality establishes a link between the concepts of military necessity and humanity. This means that the commander is not allowed to cause damage to non-combatants which is disproportionate to military need … It involves weighing the interests arising from the success of the operation on the one hand, against the possible harmful effects upon protected persons and objects on the other.’ Philippines: Air Power Manual, Philippine Air Force, Headquarters, Office of Special Studies, May 2000, paras. 1–6.4: ‘However, LOAC should not serve as an obstacle in the conduct of operations. In fact, the law recognizes the belief that the destruction of vital targets, especially if it shortens the conflict, has its long term humane effects. The chief unifying principle always applies – that the importance of the military mission (military necessity) determines, as a matter of balanced judgment (proportionality), the extent of permissible collateral or incidental injury to [an] otherwise protected person or object.’ United States: No-Strike and the Collateral Damage Estimation Methodology, CJCSI 3160.01, 13 February 2009, Glossary, GL-4: ‘Collateral damage. Unintentional or incidental injury or damage to persons or objects that would not be lawful military targets in the circumstances ruling at the time. Such damage is not unlawful so long as it is not excessive in light of the overall military advantage anticipated from the attack’ (all emphasis added; New Zealand and Philippines Manuals as quoted in the practice related to Rules 14 and 15 of the ICRC Customary Law Study, above note 2).

50 Australia: Law of Armed Conflict, above note 48, extends the precautions in attacks to protected persons, places, and objects other than civilians and civilian objects (para. 5.53). Hungary: A Hadijog, Jegyzet a Katonai, Föiskolák Hallgatói Részére, Magyar Honvédség Szolnoki Repülötiszti Föiskola, 1992, p. 45: ‘All possible measures must be taken to spare civilian persons and objects [and] specifically protected persons and objects’ (emphasis added; Hungary Manual as quoted in the practice related to Rule 15 of the ICRC Customary Law Study, above note 2).

51 United Kingdom: The Joint Service Manual of the Law of Armed Conflict, JSP 383, 2004, para. 5.32.5: ‘In considering the means or methods of attack to be used, a commander should have regard to the following factors: … f. factors affecting incidental loss or damage, such as the proximity of civilians or civilian objects in the vicinity of the target or other protected objects or zones' (emphasis added).

52 Australia: Operations Law for RAAF Commanders, AAP 1003, Royal Australian Air Force, para. 10.4: ‘When circumstances permit, advance warning should be given of attacks that might endanger non-combatants’ (emphasis added)

53 United States: Commander's Handbook on the Law of Naval Operations, NWP 1-14M, July 2007, pt. 8.3.2, p. 8-3: ‘A party to an armed conflict has an affirmative duty to remove civilians under its control (as well as the wounded, sick, shipwrecked, and prisoners of war) from the vicinity of objects of likely enemy attack.’ While this appears in the Commander's Handbook Chapter 8 on the law of targeting, it might be a reference to the precautionary obligations under the specific rules on medical units (Art. 19(2) of GC I and Art. 12(4) of AP I).

54 ICRC Commentary on the 1973 Draft Additional Protocols, above note 23, pp. 65–66 (all emphasis added). In respect to draft Art. 51 on what became precautions against the effects of attacks (Art. 58 of AP I), which again spoke only of the civilian population, individual civilians, and civilian objects, the ICRC 1973 Commentary states ‘[t]hat Party [attacked or liable to be attacked] can contribute to the safeguard of protected persons and objects in its power’, ibid., p. 67 (emphasis added).

55 Diplomatic Conference, Official Records, CDDH/III/SR.5, Vol. XIV, p. 35, para. 10, and CDDH/III/SR.21, Vol. XIV, p. 181, para. 3.

56 1969 Vienna Convention on the Law of Treaties, above note 47, Arts. 31(4) and 32.

57 Cf. above notes 12–14 and accompanying text. With regard to the obligation to verify that the objective is a lawful target, Art. 50 of the 1973 Draft Additional Protocol spoke of ensuring that the objectives to be attacked are duly identified as ‘military objectives’. No indication was found in the Official Records of the Diplomatic Conference as to why this was changed to ‘verify that the objectives to be attacked are neither civilians nor civilian objects and are not subject to special protection’ (Art. 57(2)(a)(i) of AP I, emphasis added), or why the other rules stemming from the principles of precautions and proportionality should have a less protective scope. Henderson draws an additional argument from the fact that Art. 56(1) (second sentence) of AP I expressly protects works and installations containing dangerous forces against collateral damage. This would show that ‘there are no grounds for presuming that the drafters of AP I intended protection from attack necessarily to always include protection from collateral damage. Rather, each class of object must be assessed separately’ (above note 5, p. 196). However, this argument fails to note that Art. 56 of AP I introduces a prohibition on any attack expected to release dangerous forces, not only those in which the incidental casualties and damages are expected to be excessive. The absence of such a provision for other specially protected objects only means that they are not afforded the stronger protection of Art. 56(1) of AP I, not that they should be excluded from the ‘normal’ protection against incidental damage under the principles of proportionality and precautions.

58 1969 Vienna Convention on the Law of Treaties, above note 47, Art. 31(1).

59 The paragraph on ‘Definitions’ in the San Remo Manual on International Law Applicable to Armed Conflicts at Sea states that ‘collateral casualties or collateral damage means the loss of life of, or injury to civilians or other protected persons, and damage to or the destruction of the natural environment or objects that are not in themselves military objectives’: see Doswald-Beck, Louise (ed.), San Remo Manual on International Law Applicable to Armed Conflicts at Sea, International Institute of Humanitarian Law, Cambridge University Press, Cambridge, 1995, p. 9CrossRefGoogle Scholar, para. 13(c); see also ‘Explanation’, p. 87, para. 13.9. The HPCR Air and Missile Warfare Manual, above note 22, includes ‘other protected objects’ beside ‘civilian objects’ in its definition of collateral damage in Rule 1(l), and ‘other protected persons and objects’ in its Rules 33 and 43 which concern precautions in the choice between several military objectives and precautions against the effects of attacks respectively. Specifically with regard to persons: in its Final Report to the Prosecutor, the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia mentioned ‘injury to non-combatants’ (and not ‘injury to civilians’) when speaking of incidental harm under the principle of proportionality (paras. 49 and 50); Schmitt does not distinguish between civilian and military medical personnel or those hors de combat on board medical aircraft when recalling that they have to be taken into consideration during proportionality calculation and when assessing feasible precautions (Schmitt, Michael N., ‘Targeting in operational law’, in Gill, Terry D. and Fleck, Dieter (eds), The Handbook of the International Law of Military Operations, Oxford University Press, Oxford, 2010, pp. 244–275Google Scholar, para. 18.19(1); cf. also para. 16.08(1)). More generally, when discussing the application of the principle of proportionality to medical units (though underlining the ‘permissive’ aspect of an attack which would cause non-excessive incidental damages), Bothe, Partsch and Solf state that ‘[t]he principle of proportionality is a general principle of the law of armed conflict which has found its expression in such provisions as the prohibition of “unnecessary” suffering (Article 23(c) of the Hague Convention no IV of 1907). It is not restricted to the question of the protection of the civilian population for which it has now been codified by Part IV of Protocol I’ (M. Bothe, K. J. Partsch and W. A. Solf, above note 18, p. 119). For Bartels, see above note 6.