Making the Most of Foreign Volunteers in Ukraine

ukraine foreign fighters

Editor’s note: Don’t miss our comprehensive guide to Russia’s war against Ukraine


Just days into Russia’s attack, Ukrainian President Volodymyr Zelensky announced the formation of a new military unit, the International Legion for the Territorial Defense of Ukraine. In a separate call to arms over the weekend, he stated: “Every friend of Ukraine who wants to join Ukraine in defending the country, please come over. We will give you weapons … Everyone who is defending Ukraine is a hero.” On Thursday, he claimed that 16,000 foreigners had signed up.

Foreign volunteers are hardly new to war — or to Ukraine.  While scholars have begun to study foreigners who join another government’s military, calling them “legionnaires” or “noncitizen soldiers,” this literature is still emerging. Therefore, while the persons traveling to Ukraine may not fit traditional notions of “the foreign fighter” — i.e., foreigners who travel to join insurgencies and terrorist groups — the wealth of studies on these conflict actors points to a number of possible short- and long-term implications.



To be sure, foreigners offer Ukrainian forces an immediate boost in manpower and may help stave off military defeat. However, the incoming stream of volunteers also poses a set of risks to the local population and to the volunteers’ countries of origin. The immediacy and severity of the Russian threat means that Ukraine will likely overlook any downrange risks in favor of having more friendly boots on the ground as soon as possible. To mitigate these risks, however, the Ukrainian government should ensure foreign volunteers enlist in regular combat units rather than semi-independent militias.

How Foreign Volunteers Could Help Ukraine 

In eastern Ukraine, pro-Russian separatists and government-aligned forces have been at war since 2014. Foreigners have played a significant role in these hostilities. Sources estimate that more than 17,000 foreigners from 50 countries have participated in the conflict since its onset. Of those, roughly 13,000 have joined the constellation of militant groups that make up the pro-Russian separatist forces. The remaining 4,000 foreign fighters have served on behalf of the Ukrainian government, whether in paramilitary militias or in the regular armed forces. Most are Russian, but not all. BuzzFeed recently reported that hundreds have come from the European Union, at least 40 have arrived from the United States, and at least 12 from the United Kingdom.

Ukraine’s approach to foreign volunteers has, until now, been more passive than active. That is, while the country has allowed foreigners to enlist since 2016, it has done little to further motivate their travel. Zelensky’s recent overt recruitment pitch and formal establishment of the International Legion signals, among other things, the severity of the crisis and an urgent desire to compensate for Ukraine’s poor matchup with Russia’s conventional capabilities. 

This week marks a new phase in the war. On the heels of an invasion campaign frustrated by logistical challenges, a robust defense of key positions, and a unified international response, a 40-mile convoy of Russian tanks is approaching the capitol of Kyiv and preparing for a reinvigorated assault. Russian forces have relentlessly shelled Ukraine’s second largest city, Kharkiv. In the immediate term, using the influx of foreign volunteers to support the defense of key urban areas may prove especially efficient. John Spencer, an expert in urban warfare, recently estimated that it usually takes five attackers to one defender to successfully execute an urban assault. Therefore, while it remains to be seen how many individuals will cross the border to fight against the Russian invasion force, the foreign recruits already on site carry the potential to produce an outsized tactical effect in defending Kyiv and other major cities. This would not be the first time that foreign combatants were used to increase chance of mission success in an urban campaign. For example, foreign fighters improved the lethality of al-Shabaab’s tactics during the 2010 Ramadan offensive in the Battle of Mogadishu. Similarly, foreign fighters played a key role in exploiting Russian vulnerabilities during the First Battle of Grozny.

In the intermediate term, as the war wages on and more foreigners arrive, these volunteers may affect the war’s trajectory in a number of ways. Studies of foreign fighters and foreign legionnaires alike suggest their potential impact on Ukraine’s resistance is mixed. It is conditional on a number of factors, including recruits’ degree of military experience, levels of discipline, and the command structure of the host force. In general, when foreigners join insurgencies, they help reduce the likelihood of military defeat. Relatedly, foreign recruits may introduce new skills and tactics, building on current modes of warfighting. While many travelers report no prior military experience, this war is attracting notable attention from veteran communities across the world. A team of American and British special-forces veterans are reportedly in Poland, for example, preparing to cross the border to bolster Ukrainian defenses. The arrival of experienced, high-quality recruits stands to improve Ukraine’s urban-warfare tactics and their proficiency in executing complex operations.

Managing Potential Risks

Of course, the arrival of foreign combatants is not without risk, including to the volunteers themselves. Foreigners who join insurgent or terrorist groups, for example, tend to have an especially high mortality rate. But outside recruits also raise potential risks to the local population and, upon return, to their home countries. A number of experts have already expressed concern that travelers risk exposure to violent extremist ideology. This concern is warranted; the conflict in Donbass has been marked by significant levels of neo-Nazi and white-supremacist engagement on both sides. Relatedly, there is a non-negligible risk that foreign travelers who are already radicalized will continue to attempt to travel to Ukraine for the direct purpose of receiving training and combat experience, which would make them more significant threats to their home countries.

In addition, the arrival of foreign fighters tends to correspond with higher levels of civilian victimization, including wartime sexual violence. A 2010 review of interview reports from over 2,000 foreign fighters, for example, found that those motivated by revenge and thrill-seeking were more likely to commit atrocities against civilians who they came across while serving in a foreign conflict zone. While it remains to be seen whether foreign volunteers for Ukraine’s military are similarly motivated, the consequences could be significant. Not only would these abhorrent practices exploit an already vulnerable population, they would provide Russia with new propaganda to use towards putting a moralizing veneer on their aggressive invasion. Local and international community should invest in programs to monitor for possible wartime atrocities.

Much like the character of this war, the future of the International Legion remains unclear. It will depend on Ukraine’s leaders and their ability to develop the administrative capacity to quickly process, equip, and transport foreign recruits. The Ukrainian government should work to ensure they join and fight in regular combat units. Foreign volunteers should not be permitted to form or join independent pro-government militias. Ukraine should follow through on its stated intention to formalize the enlistment process as this may help to mitigate some of the downrange risks discussed here. While not a panacea, this can facilitate positive socialization, monitoring, and accountability for recruits with less discipline or nefarious motives.

Ukraine has flung its military open wide to foreigners. As they pour in, the host may find many of their new guests to be capable and committed advocates of their cause. Foreign volunteers stand to offer a much-needed, immediate boost in manpower. But as more arrive and stay for longer, new vulnerabilities and points of friction may emerge.



Austin C. Doctor is an assistant professor of political science at the University of Nebraska at Omaha and the director of counter-terrorism research initiatives at the National Counterterrorism Innovation, Technology, and Education (NCITE) Center, a U.S. Department of Homeland Security Center of Excellence. He also serves as a non-resident fellow with the Modern War Institute at West Point. You can follow him on Twitter @austincdoctor.

Image: U.S. Army (Photo by Sgt. Spencer Rhodes)