Mercenaries on the Battlefield: What Legal Advisors Must Know

by | Dec 2, 2020

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Mercenaries … are useless and dangerous. And if a prince holds on to his state by means of mercenary armies, he will never be stable or secure…

— Niccolò Machiavelli, The Prince

Mercenaries have been used since the dawn of war. In recent years, however, there has been a tremendous resurgence in the use of mercenary forces on the battlefield. One of the most prolific employers of mercenary groups is Russia, which has used such forces to expand its presence in various world hotspots. Reliance on these opaque forces is intended to provide plausible deniability and shield Russia from responsibility. Russian practices differ fundamentally from how other nations employ private security contractors to accompany their forces. Russia’s approach represents a dangerous geopolitical trend and poses unique legal challenges in terms of State responsibility and accountability under the law of armed conflict.

Contemporary Uses of Russian Mercenaries

Russia has a long history of employing mercenaries, but under Vladimir Putin’s leadership, the practice has significantly evolved and increased. With Putin’s consolidation of Russia’s security apparatuses and an abundance of Soviet-era military veterans, the conditions were ripe for an expanded reliance on these semi-State forces. Mercenary groups provide Russia low-cost options to rapidly send forces to support favored authoritarian regimes. Russia views these groups as particularly attractive because they allow for plausible deniability. These dynamics have led to the formation of numerous Russian private mercenary groups.

The most active of these Russian mercenary organizations is the Wagner Group, which is headed by Yevgeny Prigozhin, a close Putin ally. Wagner operates worldwide despite being outlawed under a Russian law prohibiting mercenaries and private military security contractors. To circumvent these prohibitions, Wagner is registered using a series of shell corporations located outside of Russia. Its close ties to Russian security elements provide Wagner access to sophisticated weapons and intelligence. Its worldwide actions are coordinated with Russia to advance its national interests.

Wagner has been instrumental in helping Russia pursue its goals in Syria and Ukraine. In Syria, it participated alongside Syrian regime forces in offensive combat operations years before the official entry of Russian military forces. In Ukraine, elements of Wagner are suspected to have been associated with the “little green men” who supported annexation, and they have fought alongside separatist forces across the Donbass region. Russia employed these mercenaries rather than its military to avoid domestic scrutiny for casualties and, with respect to Ukraine, to falsely claim all fighters were indigenous separatists.

Russia is currently employing this mercenary model in Venezuela and across Africa as it seeks expanded influence and access to natural resources. Wagner is having a big impact in Libya where it is helping a Russian ally in the on-going civil war. Wagner’s mercenaries provided an immediate military advantage on the battlefield, tipping the balance in favor of the Russian-supported militia. The commander of the U.S. Africa Command has condemned Wagner as a “destabilizing” element helping Russia expand its African footprint.

Russia is not the only nation using these shadowy forces. The contemporary use of mercenaries is far reaching, and given the relative success Russia and others have had, one should expect to see mercenaries employed more widely in the future. Lawyers advising commanders and policy makers, therefore, must be familiar with the complicated legal framework surrounding mercenaries.

Applicable Law

The first treaty to detail the legal obligations of mercenaries is the First Additional Protocol to the Geneva Conventions (AP I). Article 47 of AP I prohibits a mercenary from qualifying as a lawful combatant and provides a six-part definition of who meets the criteria to be a mercenary. One of the six requirements is that the person must be motivated by a “desire for private gain.” The United States’ position, as detailed in the U.S. Defense Department Law of War Manual, is that being a mercenary is not a crime under international law. The manual explains that receiving pay for their services does not necessarily disqualify mercenaries of combatant status. On the other hand, mercenaries must follow the law of armed conflict and can be punished for any violations.

While the United States does not recognize the AP I position as being customary, it is important to remember that many U.S. allies are AP I treaty members and do consider it binding law. Additionally, some U.S. partners are also parties to the 1989 International Convention against the Recruitment, Use, Financing and Training of Mercenaries, which extended prohibitions against mercenary groups. Understanding partner States’ varied legal obligations regarding mercenaries will become increasingly relevant during coalition operations.

Meanwhile, Wagner and similar Russian organizations object to being labeled as mercenaries. Instead, these groups refer to themselves as private military security contractors (PMSCs). While the distinction between mercenaries and PMSCs is not always clear, Russia intentionally blurs these lines to take advantage of perceived definitional gaps.

Unlike mercenaries, security contractors do not have a separate legal classification under international law. Members of PMSCs are either combatants or civilians under the law of armed conflict. Depending on their role and affiliation with a State party to the conflict and their conduct—such as whether they are taking a direct part in hostilities—they can be classified in different ways. Legal advisors must be aware of how these varied statuses affect whether a contractor encountered on the battlefield could be targeted or detained.

The United States and many Western nations have taken steps to address some perceived PMSCs legal gaps. For instance, some States adopted a set of best practices for PMSCs in a 2008 international agreement known as the Montreux Document, which highlighted State obligations regarding security contractors. Notably, Russia refused to sign onto the agreement. Similarly, the PMSCs industry created an international code of conduct that includes a commitment by individual signatory companies to follow international law. Wagner has not yet committed to the code.

Russia has instead purposely sought to take advantage of the perceived legal gaps and use groups like Wagner to help it avoid State responsibility. Russia uses disinformation campaigns to deny any ties to Wagner and to disavow any role in directing its activities. Additionally, President Putin decreed that information related to firms cooperating with Russian intelligence would be classified. This action ensured communications between Wagner and Russian officials would remain secret.

There are many benefits for Russia if it succeeds in maintaining the illusion of separation between itself and Wagner. When Russia exclusively uses mercenary groups in an armed conflict, it can claim not to be involved in the conflict. It can thereby deflect scrutiny under the UN Charter’s non-interference principles. Furthermore, under international law, the conduct of a group can be attributed to the State if the State directs the group. Russia’s deliberate disinformation is intended to help it avoid accountability for any mercenary misconduct. Until the law potentially evolves, one should expect some nations to continue to rely on groups like Wagner.

Providing Legal Advice About Mercenary Groups

Given the growing use of mercenaries, judge advocates and civilian legal advisors must be prepared to address the thorny legal issues that arise when U.S. forces encounter them on the battlefield. The potential for such encounters is not hypothetical. In 2018, U.S. forces in Syria came under an armored assault from several hundred Wagner Group members supporting pro-Syrian regime forces. After a four-hour firefight, estimates indicate more than one-hundred Russian mercenaries were killed. With Russia expanding its worldwide mercenary presence, the potential for future such interactions with U.S. forces will only increase.

The United States also needs to highlight Russia’s illicit use of mercenaries and detail how it violates international law and facilitates corruption around the world. Legal advisors must be vigilant for law of armed conflict violations involving mercenaries as Russia’s mercenaries have been implicated in several atrocities. Judge advocates can help commands expose these abuses. With this information, America can implicate Russian State responsibility and pressure Russia to reform.


Mercenaries will play a role in future conflicts as they provide the legal ambiguity America’s adversaries seek in conflict. To prepare for future combat, legal professionals must remain attentive to these emerging participants of war. Judge advocates must also be vigilant about identifying the legal implications associated with mercenaries for their commanders.


Colonel Jeff Thurnher is a U.S. Army Judge Advocate currently serving as the Staff Judge Advocate for the 82d Airborne Division at Fort Bragg, North Carolina.