Rethinking Deterrence in Gray Zone Conflict

A particular form of international competition dominates the headlines today. Whether it is the “little green men” in Ukraine, “little blue men” in the South China Sea, Iranian backed militias throughout the Middle East, or the malicious attacks pervasive throughout the cyber-domain, scholars and practitioners agree that international competition is regularly occurring in a gray area between war and peace. The key feature of these gray zone conflicts is that actors are “pulling-their-punches” by intentionally limiting the intensity and capacity with which they conduct military operations. Rather than overt military actions that attempt to resolve issues or disputes, gray-zone conflict involves destabilization, disruption, and subversion. By engaging in the gray-zone, revisionist states can gain concessions from their adversaries while avoiding the usual costs of war. While there is much to be said on the novelty of these methods (how new is gray zone conflict?) or on their correct labeling (are these hybrid wars, non-linear wars, salami tactics, limited wars, hassling, or military operations other than war?), we focus on the implications of gray zone conflict. Does the gray zone conflict observed today actually represent a failure of Western deterrence? Or is it something different altogether?

Recent literature suggests that the conventional conceptions of deterrence are inadequate to address burgeoning threats in the gray zone. In the most basic framework of war, a state deters challengers by demonstrating how costly war would be for them. Gray-zone conflict complicates this model, as defenders can turn to gray-zone conflict to test their adversaries or gain concessions without going to war. Capable defenders, in turn, appear ill-equipped to respond to revisionism in the gray zone. While these conflicts may not be the bloodiest, they still create international instability and undermine the existing international order. In this framing, the gray zone conflict observed today constitutes a deterrence failure.

Our research challenges this convention by viewing gray-zone conflict as a symptom of deterrence success, not failure. Just as conflict is a continuum, so too is deterrence. Deterrence not only shapes whether a challenge emerges but also how challenges manifest. The more aggressive a transgression or a challenge is, the less deterrence has worked. An enemy that pulls its punches to avoid triggering a larger contest is not fighting as effectively as it might in unconstrained circumstances. Even if the challenger resorts to force, fear of escalation by the defender could cause the challenger to adopt a less productive military strategy. 

We thus have two alternative theories: gray zone conflict could represent a deterrence failure or a deterrence success. On one hand, gray-zone attacks could be the best option for a challenger, where low-level conflict can be effective and maximize cost-benefit analyses by reducing resources spent in conflict. On the other hand, gray-zone conflict might be a compromise, second-best option for a challenger, where the challenger is externally deterred from more aggressive action. 

To arbitrate these two contrasting conceptions, we can consider instances where the defender is more (or less) willing to go to war. If the challenger’s gray zone activities are more constrained when faced with a greater threat from war, then the defender has achieved some degree of deterrence success. If instead the challenger’s gray zone activities are unaffected when facing a greater threat from war, then the defender has probably failed to deter the challenger.

We find that Russian behavior in Europe is consistent with Russia being deterred. Consider the Russian interventions in Estonia, Ukraine, and Georgia, which vary in their relationship to NATO. In 2004, Estonia joined NATO. Then in 2007, Russia launched a wave of denial-of-service cyber-attacks against Estonia when a Soviet-era statue was removed. While these cyber-attacks were shocking at the time, they were addressed by Estonian domestic law enforcement, and they represent the low end of Russian gray zone aggression. Russia thus exercised relative restraint against a NATO target.

Contrast Estonia with Georgia. In 2008, Russia intervened militarily in South Ossetia and Abkhazia after NATO announced a loose pathway to membership for Georgia. Because a NATO response was so unlikely, Russian actions in Georgia were far more aggressive, deliberate, and unconstrained – Russia did not conceal the identity of its forces and used massed conventional arms. Russia retains over 10,000 troops in the Abkhazia and South Ossetia region. 

Russian activities in Ukraine represent a middle ground. In 2014, Russia invaded the Crimean Peninsula and have since supported separatist groups and engaged in ground skirmishes and cyber campaigns against Ukrainian forces. Despite this use of force over the past six years, what is happening in Ukraine falls far short of what transpired in Georgia. While NATO does not have a formal commitment to Ukraine (like Georgia), Ukraine’s geopolitical position (including its shared borders with Poland and Hungary) make it an important part of NATO’s periphery. 

In areas where NATO has greater access and interest (e.g., Estonia), Russia has greatly limited its gray zone activities. In areas with low NATO resolve (e.g., Georgia), Russia pulled no punches. Ukraine illustrates the continuum of increasing gray zone force with decreasing deterrent threat, marking a moderate level of both factors. The Ukraine case also demonstrates that Russia did indeed select its level of gray zone force based on NATO deterrence, rather than optimizing its level of aggression. Crimea is strategically important to Moscow due to the Black Sea port of Sevastopol; if Russia acted solely based on its resolve, it would prioritize Ukrainian intervention over Georgia. However, despite higher stakes in Ukraine, Russia exhibited restraint.

In addition to these case studies, we ran an analysis with a dataset of 82 Russian interventions from 1994 to 2018. The results of this analysis conform to our expectations, demonstrating that Russian gray-zone behavior does not occur despite NATO’s deterrent threat, but rather because of it. Russian gray-zone intervention is less intense in response to NATO membership. While Russia may use special operations in states that project low deterrence threats, it shifts its interference to cyberattacks or attempts at election interference in states that project higher deterrence threats.  

Even if gray zone conflict represents a kind of “deterrence success,” it is still costly, destructive, and undesirable. A natural response to the proliferation of gray-zone challenges is that NATO and its allies should be as prepared to beat its adversaries in low-level conflicts as they are in full-scale wars. Today, there is a growing consensus that  the West  should focus more resources on how to defend against gray zone attacks. Building stronger cyber walls, preparing troops that can respond to gray zone challenges, increasing the capabilities of our coast guard and air force, and preparing for a fight that does not involve direct confrontation with enemy soldiers are issues at the forefront of how the U.S. military should adapt in a world of gray-zone attacks. By building a more robust gray zone response, NATO may succeed in deterring these limited attacks in Europe.

We hope that this is the case. However, these ideas must be taken with some caution. Our research suggests that improving gray zone capabilities may be counter-productive. After all, gray zone conflict is characterized by restraint. By making gray zone conflict a worse option within the conflict continuum, the United States may find that its adversaries are less deterred against greater forms of conflict than they had anticipated. Of course, deterrence is not dead here, and it is possible to prevent adversaries from engaging in hostile acts. Specifically, by improving capabilities across the conflict continuum, NATO and its allies can prevent its adversaries from “designing around” a capable gray zone deterrent by escalating, and instead properly deter revisionist behavior.

Unfortunately, Ukraine stands today as a case of a state trying to deter an adversary primarily with a robust gray zone force. Over the past seven years, NATO has funneled assistance to Ukraine. Today, it is increasingly effective at countering Russia’s gray zone attacks. This has made the current gray zone conflict less promising for Moscow. However, what has not changed is Ukraine’s tenuous relationship with NATO and Russia’s conventional superiority. With gray zone conflict becoming a worse option for Russia, analysis suggests that Moscow today is considering the possibility of an escalated form of conflict. We hope that Ukraine’s gray zone successes are in fact encouraging Moscow to reconsider its low-level operations in the country. However, policymakers would be remiss if they did not consider the destabilizing effects that arming their allies for gray zone conflict can have when a greater war is not off the table. 

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