The Trump ascendancy, it’s safe to say, has sparked significant concern among U.S. allies. One senior German lawmaker for instance, responding to worries that the United States might not remain committed to its extended nuclear deterrence commitments, recently suggested that Europe should think about developing its own nuclear deterrent. “The U.S. nuclear shield and nuclear security guarantees are imperative for Europe,” Roderich Kiesewetter said in an interview. “If the United States no longer wants to provide this guarantee, Europe still needs nuclear protection for deterrent purposes.”

This is not a new notion. Both Charles De Gaulle and Francois Mitterand floated the idea of France extending nuclear deterrence to West Germany during the Cold War. Is this any more practical than it was forty years ago? The United States has been the only country to formally extend nuclear deterrence to others. But this idea also raises a bigger theoretical question: Could a non-superpower also credibly extend nuclear deterrence?

First, let’s be clear: There is little likelihood that U.S. security guarantees will be explicitly rescinded in the next four years, either from NATO or from Japan, South Korea, and Australia. For now, the real issue is how credible these guarantees will be in a crisis, especially given that they have rarely been articulated in the Asia-Pacific, as opposed to European, context. However, since few things are permanent in international relations, it is worth thinking through the possibilities.

The basic questions would start here: If the U.S. government does withdraw from its global security commitments in the next four to eight years, how might European security architecture evolve? In the waning light of U.S. primacy, might Germany and France (perhaps with Britain and perhaps not) become security providers for countries to their east? If so, would that mean a German finger on the nuclear trigger? Or might there be a reluctant, if not forced, rapprochement with Russia?

The same basic questions, posed against a backdrop of different geographical and historical contexts, potentially apply to Japan with respect to democratic (as well as a few other) states in Asia. Could Japan become a security provider of second resort to deter an aggressive China? Could it do so in concert with others, notably a nuclear-armed India, and if so does that portend a Japanese nuclear weapons capability?

In both Europe and Asia, the overarching question looms: Can a non-superpower nuclear weapons state like France, even in league with other states in its region, provide a European deterrent? Can India, even in league with other states in the region, do so in Asia?

There is some history here worth consulting, at least as it pertains to Europe. Back in the 1980s French President François Mitterrand considered the possibility of extending French deterrence to take into account European integration and the strategic interests of Germany. He imagined a “European deterrence” at some point in the future, but remained cautious. Alas, Mitterand knew that it was unrealistic to consider formally extending French strategic deterrence to Germany, for only the United States had the military means to make any such extension credible.¹

Credibility is no simple matter. It involves a combination of hard-to-measure degrees of political commonality among allies as well as technical capacity. In the Franco-German case of the Mitterand era, the Germans had to consider the possibility that the French proposal might pull Germany away from the United States yet be unable to really defend Germany in a pinch. The French knew what the Germans were thinking, because it was obvious—and so a degree of political distrust magnified the deficiencies in technical capability. Hence Mitterand’s caution.

If we were to really think through the possibility of a European or an Asian nuclear deterrence shorn of formal U.S. assurances, we would have to analyze a wide array of considerations, including:

• Escalation Control, Escalation Dominance
• Second-strike capability
• Flexible Response
• Assured Destruction
• Damage Limitation
• Counterforce Targeting
• Countervalue Targeting
• Limited War
• Controllability
• Crisis Stability
• C3I (Command, Control, Communications, Intelligence)

These hoary terms descend from the fact that the U.S. policymakers who contributed to fashioning the Cold War-era thinking behind the size and shape of the U.S. arsenal understood that extended deterrence was part of U.S. nuclear strategy from the beginning. Indeed, even statements from the 1950s—before ICBMs became the mainstay of nuclear delivery systems—suggest that U.S. policymakers were already considering allocating a separate, if unspecified, number of forces to deterring war in Europe. The first indicators of something resembling an extended (nuclear) deterrence “package” for East Asia emerged soon after the Korean War began. Before long, the U.S. military deployed nuclear weapons on its naval forces in the Western Pacific, and air and ground elements were based in South Korea, the Philippines, and Taiwan, with components ready to be deployed in Japan should the need for their use arise.

Under the Eisenhower Administration, the “New Look” deployment of U.S. nuclear weapons worldwide demonstrated U.S. power, commitment, and resolve against Communist forces in Europe and the Asia-Pacific. U.S. reliance on nuclear weapons shifted under the Kennedy Administration in line with the new doctrine of “flexible response,” presuming more selective targeting options. The focus very much remained on Europe, but by 1962 China attracted targeting plans separate from those designed for a general nuclear war with the Soviet Union.

Having discrete plans for using nuclear weapons outside of the central strategic deterrence of an attack on the U.S. homeland in time contributed to the development of new technologies and concepts, like “counterforce” and “countervalue” targeting and strategies. These and other concepts influenced thinking about whether a nuclear war could be “limited” and “controlled.” That, in turn, influenced the development and balance of capabilities within the U.S. strategic triad.

The point is that any country, such as France, that wishes to extend nuclear deterrence in the future would have to significantly change its current posture, which evolved without considering these issues. It could be, for example, that extended deterrence by its nature encourages larger arsenals. Is it reasonable to imagine that France would significantly expand and diversify its arsenal to ensure a second-strike capability not only for the purposes of central deterrence but for extended deterrence as well? Sea-launched ballistic missiles (SLBMs), for instance, have a crucial advantage in this respect, since they are less vulnerable to attack than land-based ICBMs and manned bombers. Would France send its force de frappe to sea in a big way? Could it?

Another important distinction is geography. Both the United States and the Soviet Union possessed vast acreage, making the notion of waging an initially limited nuclear war at least theoretically plausible. It was possible to imagine nuclear exchanges at the margins in defense of allies that left both homelands basically viable. France is probably too small for that, besides which, for that reason and perhaps others, French policymakers never accepted the notion of limited nuclear war, or riposte graduée. France instead relies on an ultime avertissement “ultimate warning,” which seems to rule out the concept of escalation control for the sake of starting-point credibility. The ability and willingness to escalate a small confrontation to higher levels of exchange is a critical component of the credibility of extended deterrence, and the ability and willingness to “fight” a nuclear war, both limited and full-scale, falls into that logic. These two elements—geography and the associated dynamics of both conventional and nuclear escalation—meant that the United States and the Soviet Union had more “time” compared to other potential nuclear dyads, both before and during a nuclear exchange. France doesn’t have these chops, and neither would Japan if it decides to go nuclear. India makes for an interesting question in this regard.

Still other issues beg attention. One is allied dialogue and communication on nuclear strategy. The NATO nuclear planning group and extended deterrence committees with South Korea and Japan since 2010 formally discuss these things. New suppliers of extended deterrence would have to establish such formal consultative bodies for their security guarantees to be credible. Communication, especially in the face of threats, is everything.

More specifically, American extended deterrence was shaped by the rigid structure of the Cold War in such a way that secondary and tertiary issues fell below the political threshold of nuclear threats and protections. In short, the number of triggers for a nuclear crisis was relatively small. But if the nuclear club in the Asia-Pacific were to grow robustly beyond North Korea, a host of new issues might multiply the number of triggers: strong emotional nationalism, territorial disputes, very asymmetric conventional and nuclear balances, the maritime context, and the vulnerability of “young” C3I systems among many.

Just as important, whereas the U.S.-Soviet engagement was both global and bipolar, engagement would be regional and multipolar, especially in Asia. Under such conditions, calculating deterrence sufficiency becomes very difficult. Smaller nuclear arsenals, too, are much more vulnerable to pre-emptive attack, and hence parties are more likely to adopt launch-on-warning or launch-on-attack postures. Each party’s nuclear doctrines, postures, and chains of command would not be clear to the other players. They might therefore be much more risk-averse, but risk aversion would probably be offset by doctrines of first-use, pre-delegation to forward-deployed and widely dispersed weapons, and geographical proximity.

The main point is that the general context of strategic interaction during the Cold War cannot be superimposed readily on other situations. Such a simple-minded superimposition was wrong when it was applied to Iraq before 2003. It was wrong when it was (and sometimes still is) applied to Iran or North Korea. And it is wrong when applied to France or Japan or any other would-be security provider.

For the foreseeable future, then, the prospects are dim for a real alternative to U.S. extended nuclear deterrence. The challenges for non-superpower nuclear weapons states like France, the United Kingdom, or India to extend such a security guarantee to four, five, or ten other states are immense, both politically and in terms of military logistics. For reasons of geography alone, there is no credible alternative to U.S. extended nuclear deterrence at the present time.

That’s not to say one could not imagine alternative nuclear orders if the current one decays. Such alternative arrangements, however, would be demanding. We may need one some day, but no one should imagine that alternatives to the existing U.S.-centric nuclear security order will pop into being fully formed should some countercultural U.S. administration decide to just walk away from legacy American obligations. Above all, the Trump Administration should imagine no such thing.