05 Apr 22. Amid much fanfare, Ukraine established a legion of foreign volunteers to help the Ukrainian people repel the Russian invasion. It seemed a logical complement to the sanctions and weapons deliveries already implemented by NATO and the international community. However, the reality was disappointing, with most volunteers sent home and further accessions limited to those with prior military experience. What can history tell us about successful foreign volunteer efforts? The answer is that some combination of screening, training, discipline, and organization are needed to produce a militarily useful force.

A Promising Initiative

President Zelensky made a plea for foreign volunteers on February 27 at the very beginning of the conflict. “Anyone who wants to join the defense of Ukraine, Europe and the world can come and fight side by side with the Ukrainians against the Russian war criminals.” Ukraine’s foreign minister elaborated on that initial plea a few days later, and Ukraine set up a website with mechanisms for foreign volunteers. By early March, Zelensky claimed that 16,000 people had signed up for the foreign legion. Given that the Ukrainian army was only 145,000 strong at the beginning of the conflict, this would have provided a major boost in strength. The foreign volunteers also provided dramatic evidence of worldwide support for the Ukrainian cause.

The Disappointing Reality

Retired Marine colonel Andrew Milburn, reporting for the online journal Task and Purpose, went to Ukraine and described how the volunteers were doing. In short, it was a fiasco. He depicted a scene of inexperience, war tourism, and idealism: “A swarm of Fantasists for every one candidate with experience in combat. And even combat experience means little in this war—because trading shots with the Taliban or al Qaeda is quite different from crouching in a freezing foxhole being pummeled by artillery fire.”

Virtually the entire first crop of recruits was sent home, as Milburn described “without ceremony or official notification.”

Faced with this disappointing result, Ukraine announced that it would limit participation to those with prior military or medical training.

The International Brigades in the Spanish Civil War

As a precedent for foreign volunteers, most commentators reached for the international brigades in the Spanish civil war. For that, it is necessary to give a little context: In the mid-1930s, Spain was experiencing social chaos after the overthrow of the monarchy and the establishment of a democratic but weak republic. Left and right fought bitterly. In July 1936, the Spanish military revolted and began a civil war.

The Soviet Union supported the republic, and the Soviet Union’s international arm, called the Communist International, or COMINTERN, began recruiting party members and others to fight. They formed national battalions to simplify communication and cohesion, and as a reflection of their recruitment by national organizations. The Americans formed the Abraham Lincoln Battalion, the French the Commune de Paris Battalion, the Italians the Garibaldi Battalion, the Germans the Thalmann Brigade, and so on.

National party leaders screened prospective applicants, although some recruits arrived individually. Units were locked in their camps for several weeks of training. Commissars enforced discipline, which was severe, with executions being common.

The informality of the organization had severe downsides. The lack of enforceable enlistment contracts or any structure for personnel administration hampered retention. The lack of formal ranks made command a democratic free-for-all.

Nevertheless, the effort produced militarily effective units, which became the shock troops of the Republican army. International brigades were critical in defending Madrid against the initial nationalist attack and later participated in every Republican offensive. About 40,000 personnel served in the brigades, though only 18,000 were present at any one time. Casualty rates were high, about 30 percent. (For a discussion of the Spanish civil war in general, see Hugh Thomas, The Spanish Civil War; for a discussion of the American volunteers, see Cecil Eby, Between the Bullet and the Lie.)

The Islamic State

The contemporary model for recruiting large numbers of foreign fighters is, unfortunately, the Islamic State. The Islamic State is rightfully known for its horrific human rights violations and intolerant ideology. Nevertheless, it was able to recruit globally and bring an estimated 40,000 foreign volunteers from 110 countries into the fight effectively. How did it do this?

As with the international brigades, the Islamic State began with a globally distributed recruiting process. Volunteers typically came through radicalized mosques where religious personnel interviewed and evaluated potential volunteers. Once volunteers passed this process, they moved along infiltration routes to the front. Before moving into the combat theater, recruits were screened again at a safe house. The Islamic State wanted to weed out the unsuitable and was understandably concerned about infiltration. Over time, the Islamic State developed a sophisticated personnel administration system to classify and compensate recruits. Once in theater, recruits received one to two months of training, both military and ideological. At the front, they typically integrated with experienced units and, unlike with the international brigades, did not form national units. The Islamic State wanted recruits to learn Arabic and identify with a unified Islamic community.

Religious fervor and the prospect of participating in a world historical event motivated the recruits. But alongside the incentives, there was also the stick. The Islamic State was known for its ferocious discipline, not hesitating to humiliate, beat, and behead problem personnel.

What Does This Mean for Ukraine?

The ferocious discipline of the Islamic State and the international brigades is not a tool that Ukraine should use. It is morally questionable, and Ukraine has claimed the moral high ground in the conflict. That leaves screening, training, and organization.

Ukraine seems to be doing both screening and training on its bases in western Ukraine. By putting new foreign recruits through a screening and training process, it can weed out the unsuitable and enhance the skills of the valuable. Ukraine needs to formalize this structure lest war tourists operate independently, make a few social media posts about their heroism and then their disappointments, and head home having added nothing but delegitimized the military effort.

Some organization is also needed. National units help cohesion and communication, though Ukrainians need some oversight through liaison officers attached to the foreign units. (Calling them commissars carries a lot of baggage, but the function of overseeing troop morale, discipline, and reliability is needed.) There also needs to be a formal personnel system for assessing skills, compensating individuals, dispensing rewards, and meting out punishment.

One purpose of any foreign volunteer operation is political, showing worldwide support for the cause and appearing to distribute the burdens. Ultimately, however, only a militarily effective force brings both battlefield advantage and international credibility. A just cause and individual enthusiasm is not enough. Producing military effectiveness requires a highly organized effort of training, supply, and personnel administration.

Mark F. Cancian is a senior adviser with the International Security Program at the Center for Strategic and International Studies in Washington, D.C.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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