Military Markings and Unmanned Aerial Vehicles

The duty to distinguish oneself from non-combatants and civilians (e.g., by wearing a uniform or distinctive emblem) is a characteristic of every domain of warfare, including the aerial environment. In naval and air warfare, the main focus of distinction is on objects, including warships and military aircraft. International law grants military aircraft a unique legal character, but to operate lawfully, they must satisfy certain conditions. One such requirement is the traditional rule regarding military markings.

Early Treatment of Military Aircraft

Military aviation emerged during turbulent times for the jus in bello. The first air platforms had limited combat capabilities, which resulted in the marginalization of airpower at the Hague Peace Conferences of 1899 and 1907. In 1899, States even tried to ban air bombardment as a method of warfare by adopting a moratorium, which was extended in 1907. (The moratorium later fell into desuetude even though, interestingly, the United Kingdom and the United States are still technically bound by it). In 1907, the only provision that could have related to air power could be found in Article 25 of the Hague Regulations, which prohibited the bombardment of undefended towns—though it is unclear the drafters had air attacks in mind at all.

However, a group of scholars at the L’Institute de Droit International, including the French jurist Paul Fauchille, seemed to better understand the potential of aircraft during armed conflict than States. In 1901, he emphasized the similarities between the status of aircraft and ships in times of war, while highlighting the uniqueness of air warfare in comparison to land warfare.  Fauchille in his previous works (Le domaine aérien et le régime juridique des aérostats) largely derived his ideas on aviation law (at that time there was no distinction between international aviation law and the law of air warfare) from the application of law of the sea provisions and concepts.

Fauchille’s main idea was to assimilate the rules of naval warfare with air warfare. The legal position of the warship and its overall characteristic (the inability to operate on land or to occupy a territory) seemed to him largely similar to the status of military aircraft. In 1911, Fauchille introduced a code on the law of air warfare in which he argued that only military aircraft have the right to be involved in hostilities. To be considered a military aircraft, the main distinctive requirement was that the aircraft had to “carry clearly distinctive and distinct markings” (Annuire L’Institute de Droit International 1911,  p. 28).

The prominent British military aviator and lawyer James Malory Spaight later expanded the research of the L’Institute de Droit International shortly before the outbreak of the First World War. Spaight proposed a definition for military aircraft according to which a military aircraft must: (1) operate under the control of the military; (2) display a visible national insignia; and (3) be manned by air crew subjected to military discipline and that respects the laws of war. The Hague Rules of Air Warfare adopted Spaight’s proposal, which remains intact today. For example, the HPCR Harvard Manual on International Law Applicable to Air and Missile Warfare defines “military aircraft” as

any aircraft (i) operated by the armed forces of a State; (ii) bearing the military markings of that State; (iii) commanded by a member of the armed forces; and (iv) controlled, manned or preprogrammed by a crew subject to regular armed forces discipline. (See also San Remo Manual Rule 13(j).)

The definition of military aircraft was actually one of the few uncontested de lege lata provisions in the HRAW of 1923. Although the Rules were not ratified by any State due to perceived problems with the regulation of air bombardment, the duty to mark military aircraft became accepted as customary international law and a constitutive element of the military aircraft definition.

The First Military Aircraft Markings

James Malory Spaight’s observations coincided with rise of the first aerial units. In 1912, French military aviation was established and a parliamentary bill set forth France’s characteristic three-color roundel. In 1913, German aviation introduced the famous Eiserne Kreuz (later Balkenkreuz) as a symbol, and in 1914, the United Kingdom’s Royal Flying Corps followed the French example by adopting similar types of markings. The American Expeditionary Forces used the color scheme of its European Allies in 1917-18.

The practice of marking by belligerents was, therefore, uniform and constant. After the war, every State that created aerial units employed unique national identifiers to demarcate their military aircraft. For example, use of a red-and-white “checkboard” emblem for Polish aviation was one of the first decisions adopted by Polish military authorities after Poland regained its independence in 1918. Characteristic color schemes, patterns, and symbols (roundel, disk, flame, checkboard, star, coat of arms) were generally used to indicate nationality and military character as required by the Hauge Rules of Air Warfare.

As noted above, the use of markings to distinguish military aircraft came to be regarded as obligatory as a matter of customary international law. The employment of emblems, flags, and insignias was already standard in naval warfare. The rule now extended to air warfare as well.

Evolution of Military Aircraft Markings during the Second World War

The Second World War confirmed the customary character of military markings. However, two varieties of this obligation began to emerge as permissible exceptions. First, the Hague Rules of Air Warfare and the practice followed during the First World War indicated that markings should be applied to all surfaces of an aircraft (bottom, top, and sides) (art. 7). However, during the Second World War, the United States marked its aircraft with the “national star insignia” in a non-symmetric way, and the Soviet Union did not paint the “red star” on the upper surface of its aircrafts’ wings, placing instead double markings on the fuselage. Later, some Warsaw Pact members similarly followed this scheme.

The irregular placement of markings is not a violation of the requirement to mark military aircraft. Rather, based on State practice, it is an accepted variety of the rule. Given the fact that aircraft designs are becoming more sophisticated, it is at times technically impossible to paint the insignia on the fuselage. The minimum requirement is that at least some marks need to be present.

Second, around this time, belligerents began to test camouflage patterns on military aircraft. For instance, Polish military aviation applied the first low-visibility markings during the invasion of Poland in 1939. In order to harmonize the intense red-and-white “checkboard” with the rest of the “Polish-blue” camouflage paint, the white of the “checkboard” was not applied to the undersides of Polish military aircraft.

Some military markings, especially very decorative insignias, are clearly inconsistent with cloaking paints. The desire to camouflage aircraft therefore forced States to consider, as Poland had done, low-visibility markings. Though still physically present, the markings are stripped of their bright and decorative elements or are applied in grey scale or in muted color palettes

Today, the military aircraft of the UK RAF, USAF, multiple NATO members, and other States display low-visibility markings. Although they are prima facie inconsistent with Article 7 of Hague Rules of Air Warfare, no State has protested the widespread use of low-visibility markings (see M. Schmitt, W. Heintschel von Heinegg, and the HPCR Manual).

Markings form a “protective umbrella” for crews operating military aircraft, including those who fly the platforms and those who control them remotely. The protecting role of the marking ensures the status of the combat crew even in the absence of uniforms. As per the HPCR Manual Commentary to rule 117, “markings of the military aircraft are sufficient indication of combatant status.” Flying in unmarked aircraft is much more risky for the crew. If a crew member is not wearing a uniform, his status will depend on whether mere membership in the regular armed forces is enough to grant the combatant privilege.

More complicated is the case of the crew member who is uniformed but flying an unmarked aircraft. In my opinion, while involved in attack, despite wearing a uniform the crew member might lose combatant status. In air warfare the duty to distinguish is fulfilled by the markings of the aircraft. For the external observer the markings on an aircraft during air combat have the same value as the uniform in land warfare. This is in line with the “protective umbrella” role of the markings: they grant even un-uniformed crew members combatant status. Undoubtedly, from the operational perspective, following both requirements—markings for aircraft and uniform for crew—is recommended (see The Law of Air, Space and Cyber Operations, p. 19).

Additionally, the customary law of air warfare does not consider flying under false markings a lawful ruse of war. In this regard it is important to distinguish between protected emblems under international law (such us the symbol of the United Nations or medical signs) and enemy markings. While killing or injury caused while using protected markings could constitute perfidy under Article 39 of Additional Protocol I to the 1949 Geneva Conventions (AP I), the use of  the enemy military markings is separate violation (as a misuse) but it is not perfidious (enemy markings are not protected emblems).

Unmanned Aircraft and Military Markings

During the Second World War, belligerents started to test the first unmanned platforms, such as the de Haviland Queen Bee, aircraft of the Aphrodite program, and the sophisticated German Luftwaffe Mistel program. Existing documentation confirms that even in cases of pilotless aircraft, military markings were still applied. After the Second World War, the practice of States started to vary. Recent photographic evidence of unmanned aerial vehicles (UAV) confirms that markings are still displayed on various unmanned platforms (e.g., Predator, Reaper).

In the ongoing Ukrainian-Russian war, Ukrainian Air Force markings are applied to the Bayraktar TB2 drone, and Russia’s older Tu-141s and Orion UCAVs display the “red star” roundel. However, smaller UAVs, like the Russian Orlan, and commercial drones deployed by both sides have not borne military markings.

It is unclear why larger drones such as the Bayraktar and Orion have military markings while smaller ones do not. Perhaps the small size of these UAVs precludes the use of such markings. However, if one could classify them as aircraft (and there are valid arguments for such a conclusion) and use them in hostilities, in order to be involved in combat operation under the law of air warfare they should fulfill the requirements of the military aircraft.

This practice of non-marking certain types of drone should be further studied in light of a possible emerging interpretation of existing rule as new types of weapons are deployed on the battlefield, such as loitering munitions or kamikaze drones. It is important to understand whether these weapons should be classified as “aircraft” in the context of air warfare. This in not very clear; some research suggests that they are “something of a hybrid between UAVs and guided missiles.” Under the DoD Directive 3000.09 (Autonomy in Weapon Systems) the loitering munition could be classified as a “guided munition.” If such devices are aircraft, then they should follow the core principle: If an unmanned aviation vehicle is involved in hostilities, it should comply with the full spectrum of requirements established by the military aircraft definition (see W. H. Boothby).

One might wonder why military markings should still be painted on in an era of unmanned aviation and the marginal role visual identification plays in contemporary air warfare. The operational function of markings as a tool of recognition is very limited in contemporary BVR (beyond-visual-range) air warfare. Typical physical markings could be replaced by ­e-markings—that is, some form of electronic or radar signature that signals the military character of the UAV. Such identification is already used in the context of medical transport.

Nevertheless, in times of war it is dangerous to rely completely on electronic, IFF systems (identification friend-or-foe), or radar signatures, as they are easily interrupted or jammed. As per visual recognition, in case of destruction, physical markings are a prima facie sign of nationality and status as a military aircraft. Thus, they serve as ultimate verification of an aircraft’s nature. This, in some circumstances, might be a fundamental factor when determining the status of the crew (as highlighted above).

Other Actors and Aircraft

It is accepted that the status of military aircraft does not exist in non-international armed conflicts. Meanwhile, in international armed conflicts, other actors besides States may engage as parties to the conflict, such as a “peoples fighting for self-determination” (art. 1(4) AP I) or an international governmental organization.

In 1960s and 1970s during the decolonization period, separatist entities such as Katanga and Biafra organized their own air detachments and adopted military markings just like States’ air forces. While by definition only States can deploy military aircraft, if a party to the conflict is recognized as a belligerent or represents the “peoples fighting for self-determination,” they should also have a right to deploy military aircraft with corresponding markings. The status of international organizations is more ambiguous. However, as showcased by the newly acquired NATO RQ-4D Phoenix UAV, the NATO Alliance also follows the customary duty to mark military aircraft belonging to the organization.

Conclusion

Even in an era of unnamed military aircraft, State practice has confirmed the customary rule requiring the marking of aircraft engaged in hostilities. However, small new UAVs and similar devices present an area for further study. It is unclear whether such platforms must also be marked.

Markings are an integral part of what defines a military aircraft, and the requirement to mark, with some light modifications, could easily apply to other types of aerial military machines. States should heed this important requirement as the omission of markings could endanger the status and protections afforded to crews operating these aircraft.

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Mateusz Piątkowski is an Assistant Professor at the University of Łódź, Poland, a Member of the Polish Society of Military Law and the Law of War, and an attorney-at-law.

Photo credit: Photo by Mary Harrsch via Flickr