NATO military capabilities and the Russian threat: A difference-in-differences analysis of the 2014 Russian invasion

BISA journal European Journal of International Security (EJIS), now offers authors the opportunity to create a video abstract or written summary for their article. In this summary, Ryan Van Wie and Jordan Becker discuss the key arguments from their new EJIS article. If you'd like to know more you can read the full article on the journal website - NATO military capabilities and the Russian threat: A difference-in-differences analysis of the 2014 Russian invasion

Introduction

Russia's invasion of Ukraine rages in its fifth year. Although Moscow has withstood withering sanctions and suffered massive losses of troops, equipment, and capital, its mobilised defence-industrial base has adapted, producing sufficient materiel to sustain its war effort while beginning to rebuild its forces.[1] In the shadow of this war, Moscow has repeatedly escalated tensions with NATO: sending drones and combat aircraft into NATO airspace, jamming GPS signals across the Baltic region, pursuing offensive cyber operations, and conducting sabotage against European infrastructure.[2]At the same time, the United States is reviewing its force posture in Europe, and many expect this may result in aconsiderable reduction of both permanent and rotational US military capabilities in the coming years.[3] Combined, the looming Russian threat and the potential reduction of US military capabilities will place renewed emphasis on European NATO members’ military capabilities. 

However, despite significant increases in NATO’s military spending—following the 2014 Russian annexation of Crimea and the subsequent NATO-wide pledge at the Wales Summit to increase defence spending to 2 percent of GDP, with a minimum of 20 percent of defence spending going to equipment—European NATO members’ average military capabilities continued to decline through 2022. Our forthcoming article in the European Journal of International Security finds that this divergence is largely geographic: after 2014, the allies bordering Russia significantly increased their troop levels relative to more distant allies, while most of the alliance continued to shrink. Notably, these frontline increases are not fully explained by higher defence spending alone, suggesting that proximity to Russia shapes how allies convert budgets into forces.

Measuring outputs, not inputs

While multiple analysts have studied how NATO defence spending evolved after 2014, little research has examined the evolution of military capabilities themselves: the troops and equipment that defence budgets are meant to produce. To fill that gap, we built a panel of 29 European countries that are now NATO members, covering 2008 to 2022. We hand-coded each country's annual active troop numbers, both military-wide and for land forces, from the International Institute for Strategic Studies' annual Military Balance report.[4] We paired these with counts of armoured vehicles and combat aircraft from Mark Souva's 2023 Material Military Power dataset.[5]

Russia's 2014 invasion alarmed the whole alliance, but some allies far more than others: those closer to Russia perceive a far greater threat than those further west.[6] To capture this variation, we employ a difference-in-differences design. In our primary specification, the treatment group includes the six allies that border Russia: Estonia, Latvia, Lithuania, Poland, Norway, and Finland. The control group includes the remaining 23 allies. Our models also account for each country's population, GDP and number of permanently stationed US troops, and, most importantly, its own personnel and equipment budgets. If frontline allies grew their forces simply because they spent more, these spending controls would capture it.

What we found

Our initial analysis shows that between the pre- and post-2014 periods, the typical European NATO member’s defence budget grew substantially while average capabilities continued pre-existing declines. Figure 1 below captures these trends. Splitting the sample by geography resolves part of this puzzle. Measured against the average trends set by the other 23 allies, the six frontline states gained roughly 9,000 active personnel and 6,000 army personnel, even accounting for what each spent on personnel. For armoured vehicles, the estimate is also positive but less precise. Because frontline fleets had already begun to expand before 2014, we read this finding as descriptive rather than causal. We find no effect on combat aircraft, which is to be expected given that Estonia, Latvia and Lithuania operate none. Several other results are worth highlighting:

• Personnel and equipment spending do not significantly predict force size in our models.
• The effect is specific to sharing a border with Russia. When we expand the treatment group to all 14 eastern European allies, it disappears.
• We see no sign that US presence crowds out allied effort. Allies hosting more permanently stationed US troops had larger armies and more armour, not less.
• In the article, we discuss three potential mechanisms that might explain the broader puzzle of shrinking NATO capabilities following increased defence spending: personnel and platform cost escalation, budget composition, and domestic politics.[7]

Figure 1: European NATO member averages, 2008–2022

Implications for European Security 

What does this analysis mean for the future of European security? In March 2025, NATO's Supreme Allied Commander Transformation warned that allies were already about 30 percent behind in delivering on existing capability targets.[8] Some analysts argue that European NATO members’ collective economic and military resources would enable them to mount a credible conventional defence against Russia without significant US support, especially if the task is defined as defending allied territory rather than launching large counteroffensives to retake it.[9] Others are more sceptical, citing major European capability shortfalls and divergent threat perceptions that would hamper Europeans' ability to pool their military power.[10] Meanwhile, Russia's mobilised defence economy has enabled it to sustain high-volume production of cheaper, less exquisite platforms, with analysts assessing that Russia could again pose a significant military challenge to NATO in the next several years.[11] 

Our findings speak directly to this debate. The 2014 Wales pledge was never meant as a spending target alone. It explicitly referred to NATO capabilities and to 'agreed output metrics' within the NATO Defence Planning Process (NDPP), which is designed to convert allied investment into the forces the alliance needs.[12] Yet, as our results show, spending can rise while capabilities continue to decline across much of the alliance, and through 2022 forces grew only where Russia is next door. Deterrence rests on capability, and whether Europe can defend itself will depend less on how much spending allies pledge than on what military forces they actually field. 

References

[1] Maria Snegovaya et al., Rebuilding to Reconquer: Can Russia's Defense Firms Deliver? (Washington, DC: CSIS, 2026), 3–15, https://www.csis.org/analysis/rebuilding-reconquer-can-russias-defense-firms-deliver. 

[2] Jin Yu Young and Anton Troianovski, “Romania Says Russian Drone Entered Its Airspace,” The New York Times, September 14, 2025. https://www.nytimes.com/2025/09/14/world/europe/romania-drone-russia-ukraine.html; Michael Schwirtz and Adam Goldman, “The Risk of Russian Sabotage in Europe: A Fight That Spirals Out of Control,” The New York Times, September 4, 2026, https://www.nytimes.com/2026/09/04/world/europe/russia-europe-nato-sabotage.html; Adam Goldman and Michael Schwirtz, “A Front Line at the Border: How Russia Uses Migrants as Weapons Against Europe,” The New York Times, October 2, 2026, https://www.nytimes.com/2026/10/02/world/europe/latvia-immigration-russia.html; Lili Bayer and Mark Trevelyan, “Russia Sends Nuclear Warning to NATO as Tensions Rise in the Baltic,” Reuters, September 30, 2026, https://www.reuters.com/business/aerospace-defense/russia-issues-nuclear-warning-nato-tensions-rise-baltic-2026-09-30/; Paul Sonne, “Tensions Escalate Between Russia and NATO’s European Members,” The New York Times, July 8, 2026, https://www.nytimes.com/2026/07/08/world/europe/russia-nato-europe-ukraine.html.

[3] 'Trump touts plan for new Poland base as Pentagon weighs Europe troop cuts', Stars and Stripes, 18 September 2026, https://www.stripes.com/branches/army/2026-09-18/trump-poland-base-europe-troop-cuts-22887147.html; 'Pentagon weighs pulling nearly a third of US forces from Europe', NBC News, 17 September 2026, https://www.nbcnews.com/politics/national-security/pentagon-weighs-pulling-nearly-third-us-forces-europe-rcna597722. 'Europe faces yearslong defense gap as US scales back, study warns', Stars and Stripes, 17 September 2026, https://www.stripes.com/theaters/europe/2026-09-17/pentagon-europe-nato-troop-cuts-22879277.html.

[4] The Military Balance. International Institute for Strategic Studies, 2008-2022.

[5] Mark Souva, “Material Military Power: A Country-Year Measure of Military Power, 1865–2019,” Journal of Peace Research 60, no. 6 (November 2023): 1002–9. doi:10.1177/00223433221112970.

[6] Matthew DiGiuseppe, Alessia Aspide and Jordan Becker, ‘Threats and the public constraint on military spending’, British Journal of Political Science, 54:3 (2024), pp. 649–66; Stephen M. Walt, The Origins of Alliances (Ithaca, NY: Cornell University Press, 1990).

[7] Keith Hartley, “Rising Costs: Augustine Revisited,” Defence and Peace Economics 31, no. 4 (May 18, 2020): 434–42. doi:10.1080/10242694.2020.1725849; Jordan Becker, Seth Benson, J. Paul Dunne, and Edmund Malesky, “Disaggregated Defense Spending: Introduction to Data,” Journal of Peace Research 62, no. 3 (March 2025): 772–88. doi:10.1177/00223433231215785.

[8] Barry et al., Defending Europe Without the United States, 12.

[9] Barry Posen, "Europe Can Defend Itself," Survival 62, no. 6 (2020): 7-34, https://doi.org/10.1080/00396338.2020.1851080

[10] Meijer and Brooks, "Illusions of Autonomy”, https://doi.org/10.1162/isec_a_00405; Mike Sweeney, "How Would Europe Defend Itself?" Defense Priorities, April 11, 2023, https://www.defensepriorities.org/explainers/how-would-europe-defend-itself/; Ben Barry et al., Defending Europe Without the United States: Costs and Consequences (London: International Institute for Strategic Studies, 2025), 4–5, 17, https://www.iiss.org/globalassets/media-library---content--migration/files/research-papers/2025/05/defending-europe-without-the-united-states/new/iiss_defending-europe-without-the-united-states_052025.pdf. 

[11] Maria Snegovaya et al., Rebuilding to Reconquer: Can Russia's Defense Firms Deliver? (Washington, DC: CSIS, 2026), 3–15, https://www.csis.org/analysis/rebuilding-reconquer-can-russias-defense-firms-deliver; Barry et al., Defending Europe Without the United States.

[12] NATO, "Wales Summit Declaration," September 5, 2014, http://www.nato.int/cps/en/natohq/official_texts_112964.htm; Jordan Becker and Robert Bell, "Defense Planning in the Fog of Peace: The Transatlantic Currency Conversion Conundrum," European Security 29, no. 2 (2020): 125–48.

Want to know more? You can read the full article at DOI: https://doi.org/10.1017/eis.2026.10095

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