After Ukraine, conventional deterrence will be the main purpose of NATO’s armed forces. NATO contingency planning, operational training and defense planning will all revolve around conventional deterrence. Russia’s ready use of force in Ukraine, Georgia and beyond shows that its non-NATO neighbors are very much at risk for military intervention. President Putin challenges the post-Cold War order by breaking the rules underlying its stability. His means include the use of covert agents to stage unrest and create excuses for Russia to intervene in the supposed name of Russian-speaking minorities. Could Moscow apply the same measures in a NATO country with a significant Russian minority population, such as Latvia? This question should keep NATO leaders up at night and by the morning they should realize that the solution is conventional deterrence.

Why conventional deterrence? A superficial structural balance of power analysis suggests that Russia will be deterred by NATO’s nuclear arsenal and will therefore not launch Ukraine-style operations against NATO members. But NATO never relied on nuclear deterrence alone. For deterrence to work, a convincing part of it must exist in time and in place. Simply put, as the ability to project power declines with distance, so does the ability to deter. An American carrier group in the Pacific is not a carrier group in the Baltic or Black Seas. Some – credible – conventional deterrence is necessary in the region. Russia is less likely to overreach if its forces cannot cross the border unharmed.

When it comes to risk perceptions, geography matters and the relevant comparison may not be between Russia’s defense budget (around USD68 billion according to the Military Balance) and the U.S. budget (around 600 billion), but between Russia and the aggregate defense budgets of Estonia, Latvia and Lithuania (around 1.2 billion). While Russia is unlikely to commit the bulk of its armed forces in an incursion against a Baltic state, Russia’s conventional advantage in the region is still decisive. Only conventional deterrence can make sure that Russian decision-makers do not come to think that they could invade NATO territory without major military costs.

The credibility of deterrence rests on the actual ability to interdict and punish any challenger. The insurance premium has to be paid for insurance to work, and the lock on the door has to be locked to be effective. NATO’s contingency plans for the Baltic countries and beyond should be backed up by a corresponding change in the Level of Ambition (NATO’s agreed force posture) as well as in extended training and exercises and a repurposing of the NATO Response Force.

In order to size and evaluate these initiatives, NATO and the wider security and defense community would do well to rediscover the tenets of conventional deterrence. In the 1980s, the strategic debate was all about the necessary force-to-space ratios on German soil. Given Russia’s recent actions, these debates will be revived in a more complicated form because of the new geography of NATO, which now includes the Baltic and Black Seas.

But conventional deterrence is not straightforward, either in practice or in theory. Some questions are linear: How to size capabilities for deterrence? How much is enough? Others are non-linear: What about political feedback loops? Can wrongly timed or sized deterrence or even the contemplation of deterrence lead to counter-reactions from Russia? Will the deployment or projected deployment of force meant to deter aggravate rather than mitigate the likelihood of a conventional conflict across a NATO border? It is important to know whether a given amount of military capability actually deters attacks – and which factors may affect it and how. Are these factors limited to the quality and quantity of military capacities? Or do they also include perceptions and psychology among the responsible leaders? The precise meanings of general, nuclear and conventional deterrence, the relationship between the different parts, and the question of predictability have all been the subjects of extensive academic, strategic and political discussions since the aftermath of Hiroshima. Developed by Bernard Brodie, Herman Kahn and more early in the Cold War, the deterrence and conventional deterrence literature blossomed in the 1980s with John J. Mearsheimer and Richard K. Betts.

Conventional deterrence in particular ties together military and political strategy. The Cold War debate about deterrence was not abstract or academic, but in fact deeply political, in ways that should be instructive to policymakers today. In Europe, the shift from the doctrine of “massive retaliation” to “flexible response” was met with serious reservations exactly because it was tied to the balance between nuclear and conventional deterrence and because it was seen to increase the risk of conventional conflict. “Massive retaliation” was based on a preference for nuclear over conventional deterrence and on the premise (or threat) that any aggression would be met with an overwhelming nuclear response. “Flexible response,” in contrast, emphasized deterrence at all levels, including the conventional. By introducing more steps on the escalation ladder it would reduce the risk of an unwanted and automatic global escalation of a conflict.

Yet critics pointed out that having more steps on the escalation ladder also increased the risk that the ladder would actually be climbed. While mutual nuclear deterrence between the U.S. and the U.S.S.R. would avert a nuclear Armageddon, a “limited” nuclear war in Europe or a conventional war, limited geographically to Europe could be made possible in this way. On the other hand, they argued, if Soviet and American leaders expected an automatic escalation to nuclear weapons, then Europe’s territory would be less likely to become the scene of a proxy conflict between the two superpowers. The transition from “massive retaliation” to “flexible response” was therefore controversial. In the same vein, military strategy options for NATO in Germany were limited by political concerns to forward defense as neither defense in depth nor offensive strategies were found politically palatable. Whatever the potential military strategic merits of defense in depth, political leaders could not accept the prospect of war across their territory. Inside NATO, conventional deterrence was therefore both a necessary part of the overall force mix and a politically contested mechanism.

In 2014 and beyond, conventional deterrence will similarly be bound and shaped as much by political as by military concerns. How will contingency planning and concomitant military preparations address the new political and military geography of the Alliance, especially in the Baltics? Will the Alliance now plan for significant, permanently deployed forces, or for residual forces and quick response forces? Does the Baltic space call for new amphibious capabilities? Will there be political consensus to develop and manage the implementation of such plans? Will NATO and its member nations be able to comprehend, communicate and coordinate such a military move within a larger grand strategy framework that both deters and engages with Russia in the long term? Will NATO and EU nations be able to coordinate such a framework? No matter how the broader strategy plays out, issues of conventional deterrence are sure to be at the heart of the discussions – both in terms of the theory and practice, and the political and military strategy, of conventional deterrence.

For the United States, the centrality of conventional deterrence means a triple challenge. The first part is getting conventional deterrence right, through U.S. and Allied armed forces, in a way that fits with a (still to come) broader strategic response to Russia. This is difficult in itself but also compounded by the second part: the transatlantic relationship. As before, conventional deterrence in Europe will be as much about the political level – dialogues as well as behind-the-scenes arm-twisting with Germany and all the other nations – as it will be about the direct military implementation. Last but certainly not least, conventional deterrence as a main focus in NATO means that America’s global alliance relationships are at stake. Taipei and Tokyo will watch closely how the U.S. and NATO deals with Tallinn, Riga, and Vilnius. As the American security establishment returns to the intricacies of conventional deterrence it will also remember the painful predicaments of making policy for the sake of credibility while having to solve the problems at hand.

(A shorter version of this essay was published at the Atlantic Council blog the New Atlanticist).

Dr. Henrik Breitenbauch is a Senior Researcher with the University of Copenhagen’s Centre for Military Studies and a Nonresident Fellow at the Centre for Transatlantic Relations, SAIS, Johns Hopkins University.

Photo credit: Medien Bundeswehr