Ukraine Symposium – Captured Enemy Weapons

The Russian military has fielded a new weapon in its conflict with Ukraine. In recent weeks, at least one frontline Russian unit was observed operating an American-made Bradley M2A2 infantry fighting vehicle, and Russia is believed to possess nearly a dozen others. Importantly, the United States did not provide the vehicles to Russia. The prized American weapon was captured from Ukrainian forces on the battlefield.

The capture and use of enemy equipment is not unusual in warfare. During the Second World War, the German military augmented its own forces with captured armored vehicles known as beutepanzers or “war-booty tanks.” In combat, individual soldiers have also frequently employed recovered enemy weapons out of necessity. Cognizant of this battlefield reality, the U.S. War Department produced an instructional film informing soldiers how to fire and maintain captured German small arms in preparation for the Normandy landings.

Although generally considered lawful, the employment of captured enemy weapons is subject to certain requirements under the law of armed conflict. This post briefly outlines some considerations.

Weapons as War Booty

The seizure of weapons from an enemy has long been recognized as lawful in war. Captured weapons become war booty or spoils of war, and under longstanding custom, ownership of the property transfers to the capturing State (U.S. Department of Defense (DoD), Law of War Manual, § 5.17.3.2).

Professor Yoram Dinstein defined war booty as follows.

Booty in warfare consists of enemy movable property that, under customary international law, may be captured on the battlefield by a belligerent party in an armed conflict. The State carrying out the capture does not have to provide any justification for its action, either on the ground of military necessity or otherwise (Max Planck Encyclopedia of Public International Law, “Booty in Warfare,” para. 1).

War booty can consist of either enemy public or enemy private movable property. In general, all enemy public movable property is susceptible to seizure as war booty. Writing shortly after the Second World War, H. A. Smith observed, “The purpose of the law of booty is to enable a belligerent to take possession of all property which his enemy can make use of for the purpose of waging war, and under modern conditions, there is very little which does not come within this definition” (p. 231). The U.S. DoD Law of War Manual explains that “public” property is property that belongs to the enemy State or an agency of that State (§ 5.17.3).

By comparison, enemy private movable property may be seized as war booty only in limited circumstances (but see, e.g., Canada Law of Armed Conflict Manual, § 622; New Zealand Manual of Armed Forces Law, § 8.10.36; Norway Law of Armed Conflict Manual, §§ 9.13, 9.40). Unlike enemy public movable property, most sources suggest that enemy private movable property may only be seized if it could be used for hostile purposes (see, e.g., International Committee of the Red Cross, Customary International Humanitarian Law Study, p. 175). Similarly, the DoD Law of War Manual limits the seizure of enemy private movable property to property that is “susceptible to direct military use, i.e., it is necessary and indispensable for the conduct of war” (§ 5.17.3). This includes privately owned weapons, ammunition, and military papers, as well as other material that could be used as military equipment, such as vehicles and communications equipment.

It is worth noting that the property of prisoners of war is generally protected from confiscation by the detaining State, although some items, including arms, military equipment, and military documents, may be seized as war booty (Geneva Convention III (GC III), art. 18). A 2020 ICRC Commentary to the Third Geneva Convention insists that “the right to capture war booty is limited to property of the enemy State to the exclusion of all private belongings of a prisoner of war,” although this does not appear to be the prevailing view of war booty (para. 1835).

When discussing arms later in the text, the 2020 Commentary deviates from its initial position, explaining that “[a]rms include any type of weapon, accessory equipment and ammunition,” apparently without regard to their public or private character (para. 1848). An earlier 1960 Commentary to the Third Geneva Convention, edited by Dr. Jean Pictet, articulated an even clearer position on arms as war booty. The 1960 Commentary included “arms of any kind” among several “[a]rticles subject to the right to take booty” and acknowledged that arms were susceptible to confiscation “whether or not they are the personal property of the prisoner” (p. 167 n.2).

Weapons Reviews and Field-Expedient Use

Once enemy arms and equipment have been taken as war booty, they become the property of the capturing State. The State may use captured property, including enemy weapons, provided the property is used in a manner consistent with international law.

The law of armed conflict clearly affirms that belligerents do not have an unlimited right to choose their means and methods of warfare (see, e.g., 1907 Hague Convention IV, Annexed Regulations (HR IV), art. 22; 1977 Additional Protocol I (AP I), art. 35(1)). This “basic tenet” of the law constrains how and even whether States may use enemy weapons captured on the battlefield.

Just as a State’s own use of weapons must comply with international weapons law, use of weapons taken from the enemy must comply with the international law applicable to the State. This means captured weapons must satisfy the State’s obligations under any weapons law treaties to which it is a party, as well as the international law applicable to armed conflict more broadly.

Subjecting enemy weapons to a methodical legal review before their subsequent fielding and use can confirm whether their use will comply with international law. Arguably, Additional Protocol I requires just such a review for States party to the Protocol. Article 36 of Additional Protocol I outlines the following weapons review requirement:

In the study, development, acquisition or adoption of a new weapon, means or method of warfare, a High Contracting Party is under an obligation to determine whether its employment would, in some or all circumstances, be prohibited by this Protocol or by any other rule of international law applicable to the High Contracting Party.

Weapons need not be “new” in the sense of newly developed or novel to be subject to review under Article 36. A 1987 Commentary to Additional Protocol I explained that arms that are “new for the State which is intending to acquire them” are also subject to evaluation under Article 36 (para. 1472). According to Col. (ret.) W. Hays Parks, the long-serving U.S. Special Assistant to the Judge Advocate General of the Army for Law of War Matters, new weapons acquired or adopted by a State include captured weapons and munitions formally reissued to its military forces (p. 114). Parks further remarked that “acquisition of a weapon or munition previously reviewed by another government does not alter the obligation of another government acquiring the same weapon or munition from conducting its own legal review” (p. 114).

Whether the requirement to conduct weapons reviews as outlined in Article 36 is also an obligation under customary international law remains an unsettled question. Some States not party to Additional Protocol I, like the United States, conduct such reviews apparently as a matter of policy. The DoD Law of War Manual notes that the U.S. policy and practice of conducting weapons reviews preceded the Article 36 requirement (§ 6.2.3).

Use of enemy weapons on a field-expedient basis, as distinct from those formally reissued and used, is not subject to Article 36 or analogous reviews (Parks, p. 114 n. 202). The review obligation appears limited to use of weapons proposed for formal incorporation into a State’s own armed forces, not weapons captured or recovered on the battlefield and hastily adopted for use in combat. The DoD Law of War Manual hints at this underlying distinction when it asserts that “captured or other foreign weapons have been used on a field-expedient basis, but otherwise have not been used in combat unless they have undergone the required legal review and have been duly issued to personnel” (§ 6.3.4; see also § 5.23.1.2).

Enemy Markings, Ruses of War, and “Perfidy”

Although not clearly an international law requirement, it is common practice for States to mark their military equipment and weapons with national and military emblems (U.S. Naval War College, Commander’s Handbook (1999), p. 508). External markings are particularly important for military vessels and aircraft, which lose certain privileges and immunities if left unmarked in peacetime (see, e.g., United Nations Law of the Sea Convention, arts. 29, 107; Chicago Convention, arts. 20, 89). During combat operations, however, the marking of vessels, aircraft, and other equipment might not be required, although this issue remains unsettled in international law (see Henderson & Cavanagh, p. 198).

The use of captured military equipment marked with enemy insignia raises a slightly different question. The law of armed conflict prohibits the improper use of the national flag, military insignia, and uniform of the enemy (HR IV, art. 23(f)). Propriety of use is circumstance dependent. According to the DoD Law of War Manual, “In general, the use of enemy flags, insignia, and military uniforms is prohibited during combat, but permissible outside of combat” (§ 5.23.1).

The deceptive use of enemy flags, insignia, and military uniforms constitutes a ruse of war when it involves no violation of the law of armed conflict and no act of perfidy. Ruses of war are expressly permitted by international law (HR IV, art. 24; AP I, art. 37(2)), but distinguishing between ruses and perfidy can be tricky. Additional Protocol I defines ruses as,

acts which are intended to mislead an adversary or to induce him to act recklessly but which infringe no rule of international law applicable in armed conflict and which are not perfidious because they do not invite the confidence of an adversary with respect to protection under that law (art. 37(2)).

Examples of ruses include the use of camouflage, decoys, mock operations, and misinformation.

Like ruses, perfidy involves deceptive acts to gain the confidence of the enemy. Perfidy, however, implicates conduct intended to betray the confidence of the enemy by convincing him that he is either protected or obligated to provide protection under the law of armed conflict. Additional Protocol I defines perfidy as,

Acts inviting the confidence of an adversary to lead him to believe that he is entitled to, or is obliged to accord, protection under the rules of international law applicable in armed conflict, with intent to betray that confidence (art. 37(1)).

Because some markings are explicitly protected under international law, their misuse could constitute an act of perfidy in armed conflict. Examples of protected identifiers include the distinctive emblems of the Geneva Conventions (e.g., the Red Cross); emblems identifying personnel engaged in the protection of cultural property; the distinctive emblem of the United Nations; and the signs, emblems, and uniforms of neutral or other States not party to the conflict.

In contrast, the national and military insignia of a party to an armed conflict are not protected identifiers under international law. Although the use of enemy insignia is likely to invite the confidence of the enemy, such conduct does not implicate the prohibition against perfidy because it does not abuse a confidence pertaining to a law-of-armed-conflict protective obligation. In other words, because the enemy is not obligated to afford protection to its own forces under the law of armed conflict, displaying the markings of the enemy does not necessarily amount to an act of perfidy.

While feigning enemy military status may not constitute perfidy, it could violate a different rule of the law of armed conflict. Displaying enemy markings when engaged in an attack could implicate the prohibition against the treacherous killing or wounding of individuals belonging to the hostile nation or military force (HR IV, art. 23(b)). This conduct is also recognized as a war crime under the International Criminal Court’s Rome Statute (arts. 8(2)(b)(xi) and 8(2)(e)(ix)). Additional Protocol I reiterates the prohibition against feigning enemy military status in attacks, but it also expands the prohibition to include conduct “to shield, favour, protect or impede military operations” (art. 39(2)). This more restrictive approach, however, is not recognized as a rule of customary international law (see U.S. DoD, Law of War Manual, § 5.23.3).

As a practical matter, the DoD Law of War Manual advises that although “immediate use of captured enemy weapons or equipment during combat is permissible,” when circumstances permit, “enemy insignia should generally be removed or alternative measures taken to distinguish U.S. forces from the enemy” (§ 5.23.1.2).

Concluding Thoughts

The use of enemy weapons captured on the battlefield is subject to certain requirements. Captured enemy weapons constitute war booty and are lawfully the property of the capturing State. Before those weapons may be issued and reused in combat, the State should ensure they can be employed in a manner that complies with international law. For States party to Additional Protocol I, a weapons review is required by Article 36. For other States, it is unclear whether weapons reviews are obligatory.

Conducting a weapons review can confirm whether captured weapons can be used in compliance with the State’s treaty obligations and the law of armed conflict. Enemy weapons employed on a field-expedient basis need not undergo a weapons review before use.

The employment of captured weapons with enemy national or military markings is not necessarily unlawful. Outside the context of attacks, the display of enemy markings can be used to accomplish ruses of war. During attacks, the display of enemy markings could violate the prohibition against the treacherous killing or wounding of the enemy. Such conduct, however, does not, per se, constitute perfidy because enemy markings are not recognized protective emblems in the law of armed conflict. Accordingly, their use does not betray a confidence regarding protected status under the law of armed conflict.

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LTC Ronald Alcala is an Associate Professor and Associate Dean for Strategy and Initiatives at the United States Military Academy at West Point. He is also Senior Military Fellow at the Lieber Institute for Law and Warfare.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

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Photo credit: U.S. Army