In response to mounting security challenges, NATO countries are trying to recruit and retain more service members, both active and reserve. At the same time, NATO is attempting to make its formations increasingly interoperable and multinational. There is one initiative that can help address both goals: integrating reserve capabilities. In doing so, NATO can both grow its forces and teach those forces how best to fight as a multinational force.

NATO has not been ignoring the potential of reserves. Many countries, especially those with conscription, have large national reserves. Finland, for instance, has only 24,000 active personnel but can reach 280,000 soldiers during wartime thanks to its active reserves. Our interview sources and reporting on individual exercises and components suggest reserves already constitute 30–40 percent of the personnel involved in some NATO exercises and make a significant contribution to multinational operations. As with most military activities, they are doing this through ad hoc task forces, fundamental skills, and can-do spirit, not a deliberate program of training.

A broader vision could also have a quantitative impact on the reserve contribution. Fourteen million Europeans (3.1 percent of the total EU population) live in a European country other than that of their citizenship, with an even higher percentage among the military-age cohorts. A collaborative program could turn this loss of potential manpower to a gain, by creating a framework to integrate former service members living in other NATO countries, either as individuals or as part of organized multinational reserve units.

Such integration could take several forms. The easiest would be to expand existing policies that allow reservists to conduct training away from their assigned units or training facilities. This could be expanded into institutional frameworks that improve collaboration and interoperability among NATO members’ reserve components. A more ambitious project would be to take this framework even further and apply the Eurocorps model to a new NATO Reserve Corps structure.

Today, most military reserve policies are of national concern; it is unusual for reservists of different national forces to meet and train together. Often, reserve components across different NATO forces are characterized by quite different career paths, training, and structure. But across these forces, a constant is that reservists help build a bridge between the civilian world and the military. When defense is left to career-oriented volunteers, instead of relying on compulsory military service, positive attitudes of civilians toward the military is critical to recruiting and retaining the necessary troops. With the deteriorating security environment, some European NATO members are bringing back the important operational role reserves play in integrated deterrence, while also seeing Ukraine as an example of the continued relevance of strategic reserves.

NATO could prevent forces from being overstretched in the critical early days of a security crisis or war by having more trained individuals on reserve status, available during contingencies. As far back as 1989, RAND research argued for increasing the number of national reserve units to offset shortages in NATO’s active forces, noting that the supply of European eighteen-year-old males was already declining. Additionally, in light of the current lack of training and readiness reported by many European countries’ reserve forces, restructuring and reorganizing reserves would offer the opportunity to conduct larger and more frequent exercises.

A more transnational reserve force would also generally improve NATO’s fighting force. Individuals would gain experience working as part of another country’s military and the sponsoring units would gain in-house liaisons and subject-matter expertise on the tactics, techniques, and procedures of an allied force.

The most basic option would build on the United States’ bilateral agreements with several allies, which allow reservists and National Guardsmen living overseas to train with local units. Within Europe, it should be relatively simple to borrow this model and expand training with units from other NATO countries. The unit hosting the reservist would simply validate the individual’s participation; the losing component would compensate the individual as it would for normal training.

A more ambitious effort would be to identify up to three countries to host a multinational reserve augmentation unit (MRAU). Individuals already under contract with a NATO member’s reserve component, but living within a reasonable distance of the MRAU, could volunteer to be assigned to it. The MRAU, commanded and logistically supported by the host country, would conduct periodic training and other activities needed to keep the assigned personnel ready for mobilization by their home countries. Additionally, the MRAU would be available to the host nation’s military units and other NATO commands to provide voluntary individual augmentation for unit training or exercises. Both the individual reservists and their home countries would clearly benefit from this situation. Because such a program would also aim to bring in expats who otherwise would remain outsides the reserves, even if they are not actively supporting operations they would be adding depth to the country’s strategic reserve.

Initially, the MRAU’s host country might expend more than it gains from this relationship. But there would be training value to having foreign reservists provide a combined dimension to wargames and exercises, and community benefits from giving resident aliens this opportunity to participate in organized local activities. If the initial MRAUs meet expectations, others could follow, at which point the initial host countries could find themselves benefiting when their own reservists become members of MRAUs elsewhere in NATO. Additionally, given the fiscal constraints most NATO militaries face, uniting some reserve components can be a cost-effective way to build strategic personnel depth quite quickly.

Among the many advantages of this program would be that the MRAUs would not be tied to a particular rank, grade, or specialty structure; they could simply accept any reservist wishing to affiliate with them. Because they would not be operational forces, they wouldn’t affect NATO’s planned structure, or take away from any other unit’s missions.

A third approach would be to create multinational operational reserve units. Because human resource management in combined forces is generally left to each troop-contributing country, either new systems capable of efficiently managing reservists from multiple countries and services will need to be created, or workarounds designed to achieve similar results. Beyond the technical challenges, reserves across NATO tend to be very different in legal status, nature of service, rank structure, and training, all of which would have to be accounted for if these reserve units are to have operational value. The fact that NATO has been working on similar issues for decades suggests the systems being used for its multinational brigades and corps may be adaptable to these new units as well. Because of these obstacles, NATO might look to the example of the Eurocorps, which began as a Franco-German unit, starting small and growing over time. This minilateral option helped the Eurocorps be a plug-and-play unit, sometimes incorporating itself into NATO’s forces.

As with any initiative of this scale, the first hurdle is bureaucratic inertia. The most basic options to encourage international training still touch on multiple laws and policies regulating assignment, pay, and legal status of service members. Even if states accepted reserve sharing as a goal, one can imagine the difficulty of resolving such issues through dozens of bilateral memoranda. NATO, however, could overcome such challenges by setting up a fund for countries to pay into or draw from, depending on whether they were net providers or consumers of combined reserve training. Alternatively, the European Union would surely invite an opportunity to reinforce NATO’s European pillar, and increase NATO-EU ties by funding some of this effort or helping set up some of the legal framework to recognize the status of reserves at least across the European Union.

Multiple sources suggest that European countries are interested in rebuilding reserve components, offering a foundation on which to pursue integration between reserve forces that can counter the inertia. Whether this integration is limited to exchange programs within NATO or geared toward creating a brand-new Reserve Corps, the time is right and the reasons for doing so are many. At a high point in transatlantic and European unity, NATO should answer the difficult question of what it actually wants from its reserves.

Stephen Dalzell is a senior defense policy researcher at the nonprofit, nonpartisan RAND Corporatioin.

Paul Cormarie is a policy analyst at RAND.

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

Image credit: NATO