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Leaders of the North Atlantic Treaty Organization (NATO) will meet for a summit in Chicago this May to conclude their Deterrence and Defense Posture Review (DDPR), which was intended to be a vehicle for resolving key questions about the future role of nuclear weapons in NATO policy. However, NATO is unlikely to resolve the question of what to do about its forward-deployed nuclear weapons before the summit.

The Alliance’s 28 member states fall along a diverse spectrum of views on these nuclear weapons, with some advocating complete disarmament and other, more vulnerable states seeking to retain these weapons indefinitely for reassurance purposes. Currently, five European countries—Germany, the Netherlands, Belgium, Italy, and Turkey—base U.S. B61 bombs on their territory and some have dual-capable aircraft that can deliver these weapons. But it is possible that some NATO allies may choose to abandon their nuclear role as they make decisions regarding successor aircraft for their own air forces. While NATO can extend the status quo for now, it cannot put off resolving its defense and deterrence dilemmas without undermining Alliance confidence and cohesion. The Alliance would be wise to establish at the Chicago Summit a process to continue work on two key issues:

1. What alternative forms of nuclear sharing and basing might be available that could simultaneously ensure wide participation in the nuclear mission, reassure those states that are seen as most vulnerable to external threat, and make a significant contribution to global disarmament efforts?
    
2. What means, if any, can be deployed to bolster non-nuclear reassurance of those NATO allies that feel most exposed to external threats? Who will provide these means and when?

We explore a range of options available to the Alliance in addressing these questions. Any policy package will need to include an agreement on alternative nuclear-sharing options (“smart sharing”) that allow for deterrence and burden sharing, while adding momentum to nuclear disarmament. A number of approaches can be envisaged for maintaining a NATO dual-capable aircraft posture in Europe, the most plausible of which provide a possible “middle way” that strikes a balance between the status quo and complete withdrawal of dual-capable aircraft.

In one scenario, some European air forces would give up the nuclear delivery capability while others retain it. Alternatively, Belgium, Germany, and the Netherlands could eliminate their dual-capable aircraft and ask that B61 bombs on their territory be withdrawn, while the United States could continue to store its bombs in Turkey and its own dual-capable aircraft and bombs in Italy. Or the United States could maintain bombs in Turkey and Italy and its dual-capable aircraft in Italy (or another European location) but assign to that unit exchange pilots from allied air forces.

In addition, the Alliance should consider measures that could compensate for the reassurance these weapons currently provide to NATO’s more vulnerable states, both to prepare for a possible withdrawal of U.S. nuclear basing in Europe and to bolster the Alliance’s overall confidence and cohesion. The more encouraging the background political-security conditions are, the less need for strong additional reassurance measures. To improve the Alliance’s security conditions, a transformation in NATO-Russia relations through transparency and confidence-building measures would have significant implications for reassurance in the Alliance, although NATO alone cannot determine this outcome. Strengthening NATO’s cohesion and refocusing on its basic collective security function would also contribute to the reassurance of the Alliance’s more vulnerable states.

We explore a variety of creative intra-Alliance measures that could bolster reassurance. These include declaratory statements by the United States and other Alliance members specifically emphasizing their commitment to the most vulnerable NATO allies and the deployment of visible reassurance measures involving some military capability in more exposed allied states. Others entail enhancing NATO’s conventional deterrence through specialized, alliance-wide improvements in capabilities; preparatory planning; infrastructure development; and exercises to enable the fulfillment of Article V obligations. NATO will continue to be a nuclear alliance as long as potential adversaries possess nuclear weapons. But the role of nuclear weapons in the Alliance’s deterrence and defense posture will continue to evolve. Following the Chicago Summit, NATO should not pause in conducting discreet and forward-looking internal consultations and studies to determine how to meet the realistic deterrence and reassurance requirements of the future strategic environment. Careful NATO management of this issue will be crucial to avoiding an entirely predictable crisis among the allies.

Introduction

The leaders of the North Atlantic Treaty Organization (NATO) are convening this May in Chicago to finalize a review of the Alliance’s deterrence and defense posture. Allied leaders, however, are preoccupied with other issues: the eurozone crisis, the war in Afghanistan, the Iranian challenge, presidential elections. Given these other priorities, and the diverse views within NATO on the long-term requirement for U.S. nuclear weapons in Europe, allied leaders meeting in Chicago are unlikely to reach a consensus on major decisions to reshape the Alliance’s deterrence and defense posture, despite significant discussions between member states over the past months. They will likely agree to extend something like the status quo, while seeking to defer fundamental questions regarding the long-term future.

Nevertheless, reckoning with NATO’s dilemmas cannot be put off much longer without undermining the Alliance’s cohesion and strength. The Alliance should in any case continue to consider how it can provide new forms of non-nuclear reassurance to its most vulnerable members. Such reassurance is useful in its own right in order to reduce uncertainty among allies about the strength of Alliance security guarantees. Moreover, in the still-likely event of future nuclear posture changes—for example, if individual allies decide that their dual-capable aircraft (DCA), which can deliver nuclear and conventional weapons, should be retired without being replaced by successor aircraft able to deliver nuclear weapons—a well-formulated menu of reassurance measures could prove important to avoid a crisis of confidence within the Alliance in the medium-term.

When in November 2010 NATO agreed to undertake a Deterrence and Defense Posture Review (DDPR), the political salience of nuclear weapons in Europe was increasing. Germany had recently called for the withdrawal of U.S. nuclear weapons from its soil; the Dutch parliament had declared that nuclear weapons in Europe were no longer needed to guarantee NATO’s security; and President Barack Obama’s April 2009 Prague speech and its aspiration for a world free of nuclear weapons were still echoing. The DDPR, to be completed for the Chicago Summit, offered a vehicle for resolving key questions about the future role of nuclear weapons in NATO policy that had not been resolved by the Alliance’s 2010 Strategic Concept.

Some states, led by Germany, wanted to eliminate the estimated 200 Europe-deployed U.S. nuclear bombs and reestablish NATO decisively in the vanguard of nuclear disarmament. Some, particularly the Baltic and certain Central European states, wanted to retain at least some of these weapons for the foreseeable future. France wanted to avoid further questioning of the vital role of nuclear deterrence. For its part, the United States wanted the Alliance to live up to its responsibility to decide collectively.

Given these persistent differences, it is likely that NATO leaders in Chicago will not make or announce decisions that significantly change the role, locations, or quantity of the Europe-deployed U.S. nuclear weapons. This is a 28-member alliance, and there does not appear to be a dependable underlying consensus on whether U.S. forward-based nuclear weapons should or should not remain in Europe. The DDPR therefore will likely put off any major changes. The NATO Summit may produce offers to Russia on transparency and confidence-building measures but will probably not be the forum for dramatic decisions on the nuclear issue.

Yet the status quo will not be sustainable for long, unless the European allies who now have nuclear-capable aircraft renew their political commitment to maintain such a capability. This seems extremely unlikely. The only U.S. and NATO “nonstrategic” nuclear weapons “Nonstrategic nuclear weapons” are also sometimes referred to as “tactical nuclear” or “substrategic nuclear” weapons. In this paper, the term nonstrategic nuclear weapons is used to include all nuclear weapons except for those that are for use on strategic delivery vehicles as defined by the New START Treaty, that is, warheads for intercontinental ballistic missiles and submarine-launched ballistic missiles, and air-launched cruise missiles and gravity bombs for nuclear-capable heavy bombers. are U.S. B61 gravity bombs. NATO member-state aircraft must be specially equipped and certified to deliver those nuclear weapons, and decisions about replacing the aging fleets in Germany, the Netherlands, Belgium, and Italy must be made this decade, even though existing planes may be kept flying longer, possibly well into the 2020s. The Eurofighter that Germany is now introducing into service as its main combat aircraft would need to be nuclear certified and fitted with the necessary avionics package to carry nuclear weapons, which the Bundestag would not support.

To avoid such a cascading loss of confidence, NATO leaders must prepare the Alliance to reach some fundamental decisions on its deterrence and defense posture after the Chicago Summit.

There is also a strong possibility that some other NATO allies (including Belgium and the Netherlands) may choose to abandon the nuclear role as they make decisions regarding successor aircraft for their own air forces. The U.S.-made F-35s that the other allies would most likely buy can be equipped for the nuclear role at a relatively small additional cost, amounting to around $5–10 million per plane. But, if Germany opts out of the nuclear delivery role and asks for withdrawal of the B61 bombs deployed on its territory, the Netherlands and Belgium are likely to follow suit. That could leave Italy and Turkey to decide whether to retain the nuclear reassurance role that at least some allies continue to find invaluable. The absence of allied consensus on nuclear policy and posture would be exposed for all to see.

To avoid such a cascading loss of confidence, NATO leaders must prepare the Alliance to reach some fundamental decisions on its deterrence and defense posture.The Alliance may be able to “get through” the DDPR and the Chicago Summit and avoid hard decisions for now. But if the Alliance does not soon address these issues and underlying political differences start to threaten the sustainability of arrangements endorsed in Chicago, it will begin to lose its ability to take collective decisions on NATO’s nuclear capabilities and policies.

For this reason, we write in advance of the NATO summit to urge member states and attentive publics to press for commitments in Chicago to a schedule and plan for resolving these issues after the summit. By establishing a process for building consensus on the issues that the DDPR will likely paper over, NATO leaders could act to maintain Alliance cohesion on this important issue.

The DDPR process has been beneficial. It has educated member states, clarified critical issues, and identified policy options. While it likely will not produce consensus resolutions on long-term nuclear issues, it has helped create the basis for decisions in the future. It would be wise to maintain momentum and press ahead over the next few years with objectives and deadlines.

This paper seeks to facilitate the onward process, first by distilling insights or conclusions that have been clarified since the beginning of the DDPR in November 2010 and then by highlighting the most important outstanding challenges that remain to be resolved. We provide some specific suggestions as to how the “appropriate mix” of Europe-based nuclear and conventional capabilities in NATO’s deterrence and defense posture might be reconsidered in coming years to reflect changing circumstances, both inside and outside the Alliance. In order to do this, we structure our discussion around key questions:

1. Given the difficulties involved in maintaining the nuclear status quo in NATO, what alternative forms of nuclear sharing and basing might be available that could simultaneously meet the requirements for wide participation in the nuclear mission and provide reassurance for those states that are seen as most vulnerable to external threat while also making a significant contribution to wider disarmament efforts?
    
2. What means, if any, can be deployed to bolster non-nuclear reassurance of those NATO allies that feel most exposed to external threats? Who will provide these means and when? If European nuclear-delivery and nuclear-basing members of the Alliance choose not to renew commitments to base and deliver forward-deployed nuclear weapons in the absence of an Alliance consensus on withdrawing, or retaining, them, how can NATO demonstrably maintain conventional reassurance, which is key to the cohesiveness on which its deterrent posture and security will continue to depend?

Addressing these pivotal, yet unresolved, issues will stir up some political controversy. However, putting off the resolution of these hard issues or papering over differences indefinitely could result in decisions by default. And, as a result, particular member states could make national procurement decisions on budgetary or political grounds that would have implications for the Alliance as a whole.

It is time for NATO to begin to consider alternatives to the status quo, so that a new consensus can be created around a revised mix of nuclear and conventional capabilities, appropriate for the new circumstances in which the Alliance finds itself.

This is not the basis on which an alliance as important as NATO can best maintain its vitality. It is therefore time for NATO to begin to consider alternatives to the status quo, so that a new consensus can be created around a revised mix of nuclear and conventional capabilities, appropriate for the new circumstances in which the Alliance finds itself.

The Current Status of NATO’s Nonstrategic Nuclear Forces and Dual-Capable Aircraft

In the 1990s, following the end of the Cold War and the collapse of the Soviet Union, the number of U.S. nuclear weapons forward-deployed in Europe declined dramatically. The reductions included withdrawal to the United States—and eventual elimination—of all nuclear artillery shells, nuclear warheads for the Lance missile system, and naval nuclear weapons, leaving only B61 nuclear gravity bombs. Further reductions of these weapons took place after 2000.

NATO decided in the 1990s to retain the combination of dual-capable aircraft and B61 bombs as the remnant of the mixed arsenal of 7,000 tactical nuclear weapons that NATO once deployed in Europe. Controversial modernization proposals involving air-to-surface standoff missiles were rejected, and DCAs with gravity bombs were judged fully capable of fulfilling the U.S. contribution to NATO’s nonstrategic nuclear weapons mission. They offer a visible U.S. nuclear presence in Europe. DCA are flexible and have the range, with refueling, to hold at-risk targets at a considerable distance. By providing and basing DCA that can deliver U.S. nuclear weapons, European allies help to spread and share the nuclear burden.¹

The United States is believed to deploy some 200 B61 bombs at six air bases in Europe for use by U.S. and allied DCA. B61 bombs are deployed at airbases in Belgium and the Netherlands for use by Belgian and Dutch F-16s, in Germany for use by German Tornados, and at two bases in Italy for use by Italian Tornados and U.S. F-16s. Although B61 bombs are deployed in Turkey, the United States maintains no DCA there, and the Turkish air force is thought to have given up the nuclear delivery mission.² (The possibility remains, if necessary, of U.S. or European DCA deploying temporarily to Turkey.) These F-16 and Tornado aircraft are expected to remain in service at least through the end of this decade.

In the post–Cold War security environment, NATO’s nuclear forces are “no longer targeted against any country … their role is now more fundamentally political, and they are no longer directed towards a specific threat,” according to an Alliance background publication on the new security environment. Although the readiness requirements for NATO DCA were once measured in hours, days, or even minutes, the Alliance decided in 1995 and again in 2002 to relax those standards. In 2004, NATO claimed that the “readiness requirements” were now measured in months.³ Even if this overstates how long it would take the Alliance to ready this capability for use were mobilization to be ordered, it is a clear reflection of NATO’s desire to signal the weapons’ primarilypolitical role.

Some believe that, in a crisis, NATO could take measures to upgrade DCA readiness. Those steps might in themselves serve a useful role in signaling Alliance seriousness and resolve. Others question the credibility of this. They note the difficulty that NATO members could face in finding consensus on raising DCA alert status, which some allies would regard as provocative and escalatory. Much would depend on the nature of the crisis in question, and in particular on whether potential adversaries had already begun to mobilize their own nuclear forces.

The presence of U.S. B61 bombs in Europe continues to play an important role in reassuring some of those allies who feel more exposed to threats that reach the Article V threshold, requiring allies to take action in defense of the threatened member state.

With the Cold War twenty years in the past, allies differ on whether U.S. nuclear weapons must be based in Europe at all in order to deter threats to NATO security. Regardless of their contribution (or lack thereof) to deterring external threats, the presence of U.S. B61 bombs in Europe continues to play an important role in reassuring some of those allies who feel more exposed to threats that reach the Article V threshold, requiring allies to take action in defense of the threatened member state. In the absence of substitute capabilities and policies to bolster confidence in NATO’s strength and resolve to defend them, these allies feel that the forward-based nuclear weapons are the best available link between the United States—and U.S. strategic forces—and their defense.

DDPR Considerations: A Distillation of the Expert-Level Dialogue

From multiple NATO and nongovernmental workshops, and numerous research reports and articles, we have distilled a number of key propositions on U.S. forward-deployed nuclear weapons in Europe. These points form the foundation for the analysis that follows.

First, the distinction between U.S. “strategic” and “nonstrategic” nuclear weapons (including those based in Europe) is now much more blurred than in the past. The 2010 U.S. Nuclear Posture Review has furthered the move away from considering U.S. nuclear bombs deployed in Europe as a means for gaining an operational advantage in a military clash, which was a central role for “tactical” nuclear weapons in Europe during the Cold War. As a result, the distinction between “strategic” and “nonstrategic” weapons is increasingly based on an arms control rationale, with the latter simply referring to those weapons that are designed to be used with delivery systems that are not currently limited under strategic arms reduction treaties. Even this distinction could become blurred in the future, should the focus of nuclear arms control transition from limitations on delivery vehicles and deployed missile warheads toward an attempt to limit all nuclear weapons, whether strategic or nonstrategic, deployed or not.

Second, at the same time, U.S. government policy still seems to be based on an assumption that there is added deterrent value in NATO’s maintenance of a variety of nuclear strike options. Some argue (though others hotly dispute) that there may be some value in having a capability to use low-yield weapons as a “last warning” before escalating to large-scale nuclear attack and/or as a means of reducing collateral damage. U.S. B61 bombs, which, according to current plans, will continue to be deployed on both B-2 heavy bombers (which are counted under the New START Treaty) and F-16 and F-35 aircraft (which are not) have a variable yield capability. The U.S. government also continues to seek a capability to attack deeply buried targets, including enemy nuclear forces and command bunkers, with accurate nuclear munitions, which could include B61 bombs on high-yield settings.

Current modernization plans for B61 weapons envisage the replacement of existing strategic and nonstrategic warhead variants with a single model (the B61-12) that will be of value for both of these roles through its combination of increased accuracy and variable yield.⁴ As a result of the post–Cold War shift in declaratory policy away from a war-fighting role—the Nuclear Posture Review calls for reducing the role of nuclear weapons and for creating conditions in which deterring a nuclear attack on the United States, its allies, and its partners would be the “sole purpose” of U.S. nuclear arms—the additional deterrent value that nonstrategic nuclear weapon capabilities provide is less than in the past. But in this way of thinking, such capabilities still have some operational, and thus deterrent, value.

Third, no purely operational or technical requirement has been publicly articulated for why B61 bombs need to be forward-deployed in Europe. Even during the Cold War, in public NATO debates there was a noticeable reluctance to discuss military rationales for nonstrategic nuclear weapons, given European concerns over nuclear war fighting on their territory. This tendency has been heightened in recent years, as the United States itself has moved to reduce the role of nuclear weapons in its defense posture.  The primary purpose of U.S. nuclear weapons deployed in Europe is now political, encompassing elements of both reassurance and burden sharing.

By reducing the stated readiness requirement for these forces to a matter of “months,” NATO has sought to emphasize that there is no short-notice military role for these weapons at present. But supporters of U.S. nuclear deployment in Europe argue that such a role could arise in the future. They are concerned that, if these weapons were withdrawn, it would not be politically feasible to return them to Europe.

Our understanding is that the role of nonstrategic nuclear weapons is now seen within NATO as providing the Alliance with a limited and uniquely configured shared initial nuclear capability. In extreme circumstances of collective self-defense, the combination of DCA with U.S. B61 bombs would allow NATO to decide, by consensus, to cross the nuclear threshold in a manner that was not purely demonstrative. Such a use of nuclear weapons would involve a target, or targets, on the territory of an aggressor but could be observably limited. The preparatory and decisionmaking steps leading up to such use would signal allied resolve to escalate further if necessary, while the combination of weapons and delivery systems would be least likely to be mistaken as forming part of a full-scale nuclear response with strategic forces.

The collective nature of the initial nuclear response with nonstrategic nuclear weapons would be further emphasized by conventionally equipped aircraft from many Alliance nations flying to support it: the Support of Nuclear Operations with Conventional Air Tactics, or SNOWCAT, mission. The nonstrategic nuclear weapons capability is therefore intended to provide an inseparable mix of operational and political utility.

The primary purpose of U.S. nuclear weapons deployed in Europe is now political, encompassing elements of both reassurance and burden sharing.

Fourth, because of the evident difficulty of establishing a unique and indispensable role, the primary purpose of U.S. nuclear weapons deployed in Europe is now political, encompassing elements of both reassurance and burden sharing. Some of the more vulnerable European allies, mainly on NATO’s eastern borders, do not want to give up what they see as an important symbol of the U.S. willingness to defend them by all means necessary. Some in the United States also think it is important for Europeans to demonstrate that they are willing to share the risks and moral burdens involved in preparing for possible nuclear use. This group of Americans would therefore dismiss the argument that there can still be a deterrent role for B61 nuclear warheads in the overall U.S. arsenal (as the U.S. government clearly still believes) but no deterrent role for these weapons when they are in Europe. Even if there is no added deterrent role from deployment in Europe, they contend that Europeans should share the task of deploying these weapons as long as they are needed. In other words, they argue, non-nuclear NATO members should not leave the moral burden of possessing nuclear weapons solely to the nuclear-weapon states, while still expecting to benefit from the protection that their membership in a nuclear Alliance brings. This argument carries less weight in non–nuclear-weapon states, which point out that all NATO’s nuclear-weapon states jealously guard their exclusive control over their national nuclear forces.

Fifth, the specific number of these weapons is of little operational importance, and the most essential numerical distinction is between zero and greaterthan- zero. For the hypothetical mixed political and operational role outlined above—a “last warning” attack that signals the prospect of further nuclear strikes, including with strategic nuclear forces—what matters for deterrence is that the United States/NATO is capable of detonating a weapon on the territory of an aggressor as a clear signal to the opponent that it must bring the conflict to an end or face escalation to a strike with strategic weapons. For this purpose, NATO only needs to ensure that a psychologically convincing minimal number, perhaps five or ten warheads, could hit targets after accounting for realistic prospects of losses to a preemptive attack or attrition by air defenses.

The subsequent total numerical requirement would then depend on how available the stockpiles in different basing countries were assumed to be in times of crisis (assuming warheads could not easily be moved in times of crisis). If, for example, planning is based on an assumption that several of the stockpiles might not be available for a nuclear strike, either for operational or political reasons, some considerable duplication of this minimum capability might be needed (for example, five stockpiles of five to ten weapons each, spread across five separate European basing countries, mean a total of twentyfive to fifty weapons).

Sixth, the total size of the stockpile is also of little importance for meeting the political (reassurance and burden-sharing) roles assigned to U.S. nuclear weapons in Europe. But it does matter for burden-sharing purposes that the stockpile is spread across a range of NATO member states and that other European member states are also involved in supporting NATO’s nuclear mission. Of course, this requirement for a wide European commitment to the nuclear role may not be vital to the purpose of reassuring exposed states, whose main concern is that U.S. aircraft and weapons will be seen to be available in a crisis. That commitment might arguably be diluted by too great a reliance on more reluctant European allies for the provision of the weapons.

The diversity of nuclear policy and posture preferences in the Alliance makes it unlikely that NATO will agree, as part of the outcome of the current DDPR, to substantially reduce the number of its forward-deployed nuclear weapons in the absence of some form of Russian reciprocation. Beyond the DDPR, the smaller the number of basing countries, the harder it may be to maintain domestic political support for continuing the nuclear role. Thus, a renunciation by one state—for example, Germany—of the nuclear-hosting role might lead others—for example, the Netherlands and Belgium—to renounce this role too. These decisions would reduce the number of basing states from five to two and could increase pressure on the Italian and Turkish governments to consider giving up hosting U.S. nuclear weapons as well. Yet, a further downward  trend in the number of nuclear weapons could have some benefit as a signal of disarmament commitment. As in the case of any deterrent role, however, the primary political distinction is between having zero or more-than-zero U.S. nuclear weapons in Europe.

Seventh, as a general rule, the physical location of nuclear weapons— whether Russian or American—matters much less militarily than in the past. But physical location does make a political difference in peacetime. It is bound up with the collective nature of NATO’s nuclear deterrent posture, which Alliance statements emphasize as a unique strength. Some of NATO’s newer member states appear to attach particular value to the tangible symbol of the U.S. nuclear guarantee that Europe basing provides. At the same time, the physical proximity of nuclear weapons in the westernmost parts of the Russian Federation also has an intimidatory effect, especially when accompanied by an aggressive declaratory policy on the part of Russian leaders.

Eighth, this is not primarily a budget-driven debate. The expenses involved in modernizing aircraft are small compared to national air force budgets, even more so compared to total NATO collective military expenditures. The United States has indicated it will go on meeting the more considerable expenses involved in developing, producing, servicing, and protecting the bombs. If the nuclear posture is changed by individual national parliaments refusing financial approval, it will be because of a political rejection of involvement in the DCA mission, expressed through line-item vetoes. In no public forum, for example, has any German official or commentator conceded that if NATO money could be found for the nuclear modification and certification of German Eurofighters it would make the slightest difference to the acceptability of the idea within the Bundestag.

Ninth, the prospect of sharp reductions in U.S. conventional forces in Europe could have a significant impact on the debate on the future of U.S. nuclear weapons on the continent. The United States has made clear that it wishes Europe would become more of a “provider” of security than a “consumer” and that the role for residual Europe-based U.