Combatants Dressed as Civilians

The Case of the Israeli Mista’arvim under International Law

English Policy Paper No. 8

  • Written By:
  • Publication Date:
  • Cover Type: Softcover
  • Number Of Pages: 82 Pages
  • Center: The Amnon Lipkin-Shahak Program on National Security and the Law
  • Price: 45 NIS

An overview of the history of the <em>Mista’arvim</em>—elite units of Israeli soldiers disguised as local Arabs—that analyzes the legality and implications of the use of such undercover units for law enforcement and combat operations under international law.

This policy paper provides an overview of the history of the Israeli undercover units known as Mista’arvim—elite units of Israeli soldiers who operate in the West Bank and Gaza while disguised as local Arabs—and analyzes the legality and implications of the use of such units for law enforcement and combat operations under international law.

This policy paper asserts that undercover operations are not prohibited under international law per se, unless they violate principles of international law or constitute a war crime such as perfidy. In addition, it presents practical and operational conclusions and includes recommendations to guide Israel’s military forces in the deployment of undercover units. 

This policy paper was written under the guidance of Prof. Yuval Shany as part of IDI’s National Security and Democracy project, which was headed by Prof. Shany and Prof. Mordechai Kremnitzer. Today the project is headed by Admiral Amichay (Ami) Ayalon and Prof. Mordechai Kremnitzer.



Chapter 1: Undercover Units    

1. Working Definition    
2. History    
3. Contemporary Use of Undercover Units    
4. Israel’s Use of Undercover Units—Mista’arvim    

Chapter 2: Operations of Undercover Units as Combat Actions

1. The Requirement to Wear Uniforms

1.1. Distinction
1.2. Taking a Direct Part in Hostilities
1.3. International Armed Conflict
1.4. Non-International Armed Conflict
1.5. Conclusion    


2. Perfidy and Treacherous Killing or Wounding    

2.1. The Elements of Perfidy    
2.2. Deployment Preceding an Attack    
2.3. Failed Attempts    
2.4. The Differences between Perfidy and Treachery    
2.5. The Customary Nature of Perfidy    
2.6. Application in Non-International Armed Conflict    
2.7. Ruses of War    
2.8. Application to Asymmetric Warfare    
2.9. Conclusion

3. Espionage

4. Undercover Unit Operations under IHL

4.1. Conclusion    

Chapter 3: Operations of Undercover Units in Mixed Actions

1. Classification of the Legal Framework

Chapter 4: Implications of Undercover Operations

1. POW Status    
2. Investigations    
3. Liability    

Chapter 5: Analysis of Specific Situations: Test Cases    

1. Undercover Unit Action in Ramallah (January 4, 2007)

1.1. Background Information    
1.2. Analysis    

2. Operation Two Towers (June 20, 2007)

2.1. Background Information    
2.2. Analysis    

Chapter 6: Conclusions    

Chapter 7: Recommendations   

Military operations involving soldiers wearing civilian clothes have always been employed by state security and military forces. Records of undercover military activity date back at least to World War II and such activity continues until the present. In the Israeli context, these units are called Mista’arvim since they dress up like local Arabs when they operate in the West Bank and the Gaza Strip, usually for counter-terrorism purposes.

Though commonplace, the employment of undercover units raises difficult questions with regard to law and ethics. In the context of armed conflict in particular, the lawfulness of using undercover forces has been questioned, as it might be perceived to be a violation of the prohibition of perfidy or other forms of treachery tantamount to war crimes.

Military operations can fall either under the law-enforcement or combat paradigms. Law-enforcement operations are subject to international human rights law (IHRL) and combat operations are subject to international humanitarian law (IHL, also known as the laws of armed conflict). Within IHL there are several differences between international armed conflict (mostly referred to as classic inter-state conflicts) and non-international armed conflicts (mostly known and referred to as situations of civil war). One of the main and relevant differences between international and non-international armed conflicts is the lack of combatant status in non-international armed conflicts. This means that there is no combatant immunity or prisoner of war (POW) status in such conflicts.

Undercover operations raise several issues under international law:

  1. The failure to comport with the requirement that combatants wear uniforms or other distinctive signs derived from the principle of distinction;
  2. What is the legal framework of undercover combat operations? Are they permitted ruses of war, prohibited perfidious or treacherous acts, or legitimate acts of espionage?
  3. What are the implications of such operations? Do they have an effect over the right to POW status, the requirement to open an investigation and the question of liability for the results?

The principle of distinction is one of the core principles of IHL, and the requirement to operate while wearing a uniform or a distinctive sign is generally considered one of the fundamental criteria for attaining combatant status. However, after examining the relevant sources such as the Geneva Conventions and their additional protocols, we have concluded that the mere operation of combatants without uniforms does not violate IHL. Nevertheless, since that requirement is also one of the basic conditions for conferring POW status upon combatants, the failure to wear a distinctive sign while conducting a military attack could result in the loss of the right to POW status in international armed conflicts, and thus the loss of combatant immunity. Furthermore, while the lack of a distinctive sign does not constitute a violation of IHL per se, it could serve as an element of an IHL violation, such as perfidy or treachery.

The prohibition of perfidy and treachery is based on the existence of trust between adversaries in armed conflict, and a breach of such trust, by means of, inter alia, feigning the status of a protected person (such as an uninvolved civilian) in order to kill, wound or capture a person. The rationale for such prohibition rests on three main and fundamental notions: distinction, chivalry, and reciprocity.

After analyzing the prohibitions and their elements, we have reached the following conclusions:

  • Customary nature of the prohibition – Treacherous and perfidious killing or wounding, originating in article 23 of the 1907 Hague Regulations and article 37 of Additional Protocol I, are customary prohibitions under IHL and are applicable to all parties in international and non-international armed conflicts. The prohibition against capturing a person while resorting to perfidious ways, appears only in article 37 of Additional Protocol I and does not constitute a customary prohibition, and therefore, it applies only to states party to Additional Protocol I.
  • The mere use of undercover units does not constitute a violation of the prohibition of perfidy and treachery. Only undercover operations aimed at the killing or wounding of an adversary are prohibited as perfidious and treacherous.
  • The violation of the prohibition of perfidy and treachery becomes applicable from the point that the undercover forces are de facto visible to the adversary during the deployment to attack, and therefore trust can be established.
  • Undercover operations aimed at the gathering of information are not prohibited as perfidious or treacherous acts and could be considered acts of espionage.

In mixed situations of law-enforcement and combat operations, such as during belligerent occupation, both law-enforcement and combat operations can take place. As the applicable law is different in each context, the correct choice of applicable law is of the utmost importance. In certain situations, the military government conducts “law and order” operations (law enforcement)—military actions to deal with moderate levels of violence, which are more akin to the challenge posed by crime-suppression activity and are governed by international human rights law. In other violent contexts in which a nexus to an ongoing or new armed conflict can be established, the occupying power may engage in combat action, which is governed by IHL.

In law-enforcement actions there is no positive restriction on the use of undercover units. The only relevant requirement is to conduct operations in accordance with the law, and especially to ensure that the use of force (and especially lethal force) takes place only as a last resort and under appropriate circumstances.

In order to identify what operations would constitute law-enforcement operations, we need to examine the entire situation and take into account all of its characteristics, including:

  1. The intensity of the hostilities
  2. The aim of the operation
  3. The identity of the target of the operation
  4. The proximity to the battlefield
  5. The location of the operation
  6. The identity of the operating force.

It should be noted that these characteristics are not meant to serve as an exhaustive or cumulative list of conditions for the identification of an operation as either law-enforcement or combat action. Such examination can provide the military authorities with an ex ante understanding of the applicable legal framework.


Conducting operations using undercover units may have several implications under international law:

  1. POW Status – If undercover combatants are caught while operating undercover in an international armed conflict, they may lose their entitlement to POW status and the privileges that come with it–e.g., they may be put on trial for the mere participation in hostilities as well as any other violation committed by them under domestic and international law (such as the killing of an adversary). However, we have also concluded that if the combatants are caught after regaining distinction, their rights remain untouched and they can be tried only for violations and not for the mere participation in hostilities.
  2. Investigations –The obligation to investigate alleged wrongdoings is different under IHRL and IHL—this difference is evident when considering the reasons to initiate an investigation. Under IHL, there is a clear requirement to investigate allegations and suspicions of grave breaches of IHL and war crimes. There is no obvious need to investigate conduct that does not result in damage to property or harm to civilians. Under IHRL, the obligation to investigate is broader and requires an investigation of any suspicion of gross violations of human rights–such as the use of lethal force. Therefore we suggest that in the wake of undercover operations resulting in death or injury (even of legitimate military targets) conducted either under the law-enforcement paradigm or the combat-action paradigm, an investigation should be initiated to examine possible violations of the law, including the law against perfidy/treachery.
  3. Liability –When undercover units operate under law-enforcement or combat paradigms, the members of the undercover units are responsible for their actions. In both international and non-international armed conflicts, captured members of undercover units may be prosecuted for their direct participation in hostilities under the domestic law of the state that captured them. When operating under the combat-action paradigm, combatants are also prohibited from violating IHL, and especially from committing grave breaches and war crimes.

    While treacherous and perfidious acts may constitute a war crime, it seems that without prejudice to the customary nature of the prohibition on capturing by means of perfidy, neither Additional Protocol I nor the Rome Statute of the International Criminal Court include it in the list of criminal prohibitions. It seems reasonable to conclude that even with regard to states party to API, violating the prohibition on capturing through treacherous means by undercover units would not amount to a war crime and therefore could be categorized, at most, as an “ordinary” violation of IHL or an “ordinary” crime.

    The war crime of treachery has two elements: (a) an objective element—the act must objectively be of a nature to cause, or at least to induce, the confidence of an adversary; and (b) a subjective element—the act inviting confidence must be carried out intentionally in order to mislead the adversary into relying on the expected protection. Moreover, in order for the act to be considered a crime, a prescribed end result (death or injury) must ensue.

    Because of the requirement that the act involve confidence building, both the objective and subjective elements can be met only when there is some contact (mainly visual) between the attacking forces and the adversary. Therefore, attacks from a great distance (such as sniper attacks) or surprise attacks (such as ambushes) would fail to fulfill this element of the crime.

    There is no need for precise identification of the targeted adversary in order to raise suspicions of perfidy. Hence, if during deployment, the undercover unit takes advantage of the feigned status in order to intentionally cause the death or injury of an alternative adversary (a person other than the original target), the elements of the crime might be fulfilled. On the other hand, if the intent of the operation is not to cause physical harm to the adversary, then the act most likely will not meet the definition of treachery under the Rome Statute.
  1. Undercover operations should be conducted for purposes of information gathering or to capture persons – An undercover combat operation aimed at the killing (or injuring) of an adversary could be considered as treacherous or perfidious and, therefore, should be avoided. While undercover operations for the destruction of military objectives are permissible as well, such operations can be conducted as long as no person is expected to be killed or injured as a direct result of such an operation.
  2. A Mista’arvim unit must distinguish itself from the de facto visibility point – IHL does not contain a positive requirement to wear a distinctive sign or uniform. However, in order to avoid perfidy or treachery violations, Mista’arvim units must carry their arms openly and wear distinctive signs from the first point of the deployment that is visible to the enemy. This does not mean that the units are prohibited from wearing camouflage or from acting in any other way in accordance to IHL rules.
  3. In case of escalated law-enforcement operations, undercover units should be identified – The tests for the legal paradigm movement from law enforcement to combat action are both vague and complicated to compute in the midst of the escalated operation. Once a law enforcement operation escalates into a possible combat action, in order to be certain that no treacherous killings occur, the operating forces should reveal distinctive identifying signs.
  4. Conduct investigation in cases of death or injury Whenever an undercover operation resulted in the death or injury of a person, such an outcome should serve as a sufficient basis for the opening of an investigation to examine the reasons for such a result. Such an investigation ought to be conducted in accordance with the relevant standards under international law (genuine, effective, impartial, prompt and transparent).

The fulfillment of these recommendations will help to ensure that the deployment of undercover units remains within the international law framework and to ensure respect for the special protections provided by international humanitarian law and to reduce the loss of life of uninvolved civilians during such operations

Adv. Ido Rosenzweig, a former researcher at the Israel Democracy Institute, is co-founder and chairman of ALMA – The Association for the Promotion of International Humanitarian Law in Israel, and is the Director of Cyber, Belligerencies and Terrorism Research at the University of Haifa’s Minerva Center for the Rule of Law under Extreme Conditions.