Ø In the event of the United States retreating into isolationism, Germany would be deprived of the US’s implicit nuclear guarantee. All other things equal, this would weaken Germany’s security and force Berlin to make difficult decisions with respect to its security and nuclear policy.
Ø In such a scenario, Germany has three basic options: (1) Forego a nuclear deterrent altogether; (2) enter into some sort of renewed and credible nuclear sharing arrangement with a third country (or group of countries); or (3) create a robust, independent national nuclear deterrent.
Ø All three options generate varying strategic and political costs and benefits. Combining a latent (potentially enhanced) nuclear capability with a credible nuclear sharing arrangement (with France) would help minimize costs, while largely preserving the strategic benefits of nuclear deterrence.
What if the United States pulled out of NATO and Germany had to do without the US nuclear deterrent? Although this would (arguably) be a major unforced error on the part of the United States, such a scenario cannot be dismissed out of hand after the Trump administration – bluff or no bluff – threatened to leave NATO. In a recent paper[1], we explored three scenarios with respect to future US grand strategy, one of which outlined the possible consequences of a US turn towards isolationism. In such a scenario, the United States would end the forward deployment of its military forces in Europe (and East Asia), leave NATO and terminate its commitment to European security, including extended nuclear deterrence. However unlikely such a scenario may (or may not) appear[2], its implications are worth examining. A withdrawal of the US nuclear guarantee would force Germany to review both its conventional military posture and its stance towards nuclear deterrence.
Historical background
Nuclear deterrence was a crucial pillar of West German security during the Cold War. While Germany never acquired an independent nuclear deterrent, and multilateral nuclear deterrence proposal came to naught after the failure of the Multilateral Force (MLF) [3], it benefitted from US (and UK) extended nuclear deterrence. West German security hinged on a US commitment to respond to a conventional or nuclear attack on Germany with nuclear retaliation. This was arguably crucial in view of USSR and Warsaw Pact conventional superiority. While counterfactuals cannot be proved one way or the other, extended deterrence – it can be argued on logical grounds – contributed to the absence of armed conflict between NATO and the Warsaw Pact, and thus benefitted West German security enormously[4]. After all, West and East Germany would have been the main battleground in case of both a conventional and nuclear conflict.
In the 1970s, the credibility of the nuclear guarantee was being undermined by the deployment of Soviet nuclear intermediate-range missiles. The NATO double-track decision, namely, the deployment of Pershing-II missiles, sought to shore up nuclear credibility by preserving credible deterrence at the sub-strategic level, while eliminating the risk of potential nuclear blackmail. All of this is to say that nuclear deterrence was a key element of West Germany’s security strategy and nuclear policy was always an issue that German decisionmakers had to wrestle with (e.g. Adenauer/ Strauss). Although the Cold War ended three decades ago and Germany is today surrounded by allies, Germany continues to benefit from US extended deterrence in the guise of the so-called nuclear sharing agreement that provides Germany with have access to nuclear weapons in case of an armed conflict. Through NATO, Germany also continues to benefit from at least an implicit US nuclear guarantee in the guise of collective security. Extended deterrence, including the nuclear sharing agreement with the United States in the context of NATO, would become obsolete in case of an American retreat into isolationism. After all, the UK nuclear deterrent is highly dependent on the US and therefore, arguably, of limited credibility[5].
Strategic Background, Rationale and Logic
The crucial question is (1) whether, strategically, Germany needs a nuclear deterrent and, in case the United States withdraws from NATO, (2) if such a deterrent can be made effective and credible and, if so, (3) at what strategic, political and economic cost. During the Cold War, Western nuclear deterrence initially sought to offset Warsaw Pact conventional superiority and, once the USSR acquired an increasingly potent nuclear arsenal, maintain mutually assured destruction (aka nuclear balance). In the 1980s, NATO strategy increasingly looked to nuclear weapons as deterrence as well as war-fighting instruments[6]. Today, Russian conventional forces represent less of a threat to German security than during the Cold War – in spite of recent Russian military modernization. The rationale for a German nuclear capability would therefore be somewhat less to deter a conventional attack on Western Europe, but rather – following the logic of the nuclear revolution – to deter any attack, whether conventional or unconventional, and thereby eliminate the security dilemma altogether[7]. Full disclosure: the so-called stability-instability paradox posits that mutually assured destruction, while preventing direct armed conflict between nuclear powers, raises the likelihood of minor, indirect, conventional armed conflict between them.
If and to what extent non-nuclear states face the possibility of nuclear coercion by nuclear states is a crucial question in this context. The “coercionist school” posits that nuclear blackmail works (or can work), as it increases both the likelihood of coercion on the part of the nuclear-armed state vis-à-vis a non-nuclear state and creates incentives for brinkmanship on the back of escalation dominance[8]. An opposing school of thought regards the use of nuclear weapons as a coercive instrument as tactically redundant, costly and, ultimately, as lacking in credibility given the necessarily limited issues at stake. Whichever side one comes down on in this debate, it is difficult to dispute that a non-nuclear state is at least potentially weaker and more vulnerable than a nuclear state, particularly if the nuclear state can exploit the other side’s conventional inferiority[9] - now or in future. While a nuclear power cannot be coerced militarily by another nuclear power, let alone by a non-nuclear power, a non-nuclear power may be at risk of coercion attempts. Either way, a credible nuclear deterrent definitely helps preempt the possibility of nuclear coercion by another nuclear state as well as exploitation of one’s conventional military inferiority by such a state. Strategically speaking, minimum, narrow deterrence[10] would suffice to eliminate the risk of nuclear and conventional military coercion by another nuclear state.
Of the four reasons to acquire military capabilities – deterrence, compellence, defense, swaggering – nuclear weapons certainly lend themselves to deterrence and swaggering[11]. The strategic rationale underpinning minimum deterrence is, again, less to coerce (compellence) another state or even to actually retaliate (defense) in response to a conventional or nuclear attack than to deter such an attack in the first place. Again, minimum deterrence helps limit strategic vulnerability that is at least a potential source of influence for an opposing, nuclear-armed state. Ultimately, the underlying strategic rationale for the acquisition of a nuclear deterrent is the elimination of the security dilemma between two states with robust nuclear deterrence – the stability-instability caveat notwithstanding.
Costs and Benefits of Various Options
In light of these strategic considerations, Germany has three broad options, and each comes with different costs and benefits attached: (1) retain a latent nuclear capability, that is, retain the ability to produce and deploy on relatively short notice an effective nuclear deterrent; (2) replace the US guarantee with another guarantee and/ or renewed nuclear sharing with another country or group of countries; (3) deploy an independent national deterrent.
All three options generate varying costs and benefits, risks and opportunities. Option 1 fails to address Germany’s actual or potential strategic vulnerability vis-a-vis nuclear powers and it fails to eliminate the security dilemma. Option 2 limits strategic vulnerability but, at a minimum, raises the issue of credibility. If in a bilateral or multilateral arrangement Germany does not control an independent nuclear deterrent and continues to depend on somebody else’s permission to use them, the credibility of the nuclear deterrence may be constrained (much obviously depends on the details). The country offering extended deterrence needs to have a robust and credible nuclear deterrent itself. Otherwise extended nuclear deterrence lacks credibility in the first place. Option 3 offers the greatest degree of credibility, provided a robust nuclear posture, including effective second-strike capability, can be put in place. It is also going to be the costliest option in international and domestic political terms as well as economic terms[12].
How these costs are assessed and weighted will in part be a function of the international security environment. Roughly speaking, the domestic and international political costs increase from option 1 through option 3, while the strategic benefits in terms of credible and effective nuclear deterrence increase. The potential international political costs depend on the reaction of other countries to a German nuclear capability, including second-round effects such as the spread of nuclear weapons[13]. Last but not least, deploying an independent national nuclear deterrent would obviously create the greatest challenges in operational, technical and domestic (aka widespread opposition, potentially undermining credibility) and international (aka violation of existing treaties committing Germany not to develop, produce or deploy nuclear weapons) political terms[14]. Decision-makers facing difficult choices in the event of a US turn towards isolationism need to weigh these costs and benefits carefully.
A sensible compromise might be to opt for option 2 (nuclear sharing, joint deterrence) given its limited domestic and international costs, limited technical and operational challenges and manageable international security environment. Essentially this would maintain the status quo. A nuclear sharing agreement with France would be slightly weaker than the present NATO/ US arrangement, but it should be sufficient to guarantee minimum deterrence. It would also avoid the violation of international treaties and would be more palatable for third countries, including France, Germany’s Eastern European partners and Russia – even the United States. Again, it would largely be an extension of the status quo.
Option 2 could be combined with option 1 (aka enhanced, latent capability) if policymakers are concerned about a substantial deterioration of the international security environment. In this case (aka increased risk of nuclear coercion and mounting conventional inferiority vis-à-vis a nuclear-armed power) as well as in case the credibility of extended deterrence diminishes for whatever reason, putting in place the conditions to produce and deploy a robust (!) and credible (1) nuclear deterrent on short notice would provide a strategic hedge. Naturally, technical (technology) and operational (training, posture) problems would need to be sorted out. A necessary second-strike capability would likely require the deployment of nuclear warheads on submarines geared towards counter-value strikes. Enhancing Germany’s latent nuclear capability would violate German commitments under the Non-Proliferation Treaty and the Two-Four Treaty, and hence generate an international and domestic political backlash.
Hedge nuclear (multilateral) sharing with independent option
The details of any future scenario where the US turns towards isolationism will matter. The specific relative strategic and political costs and benefits associated with the three options may therefore vary. Strategically, much will (and should) hinge on how vulnerable Germany would be to conventional and non-conventional security threats, following a US withdrawal, how credible and reliable nuclear sharing would be relative to the domestic and international political costs and operational challenges related to the creation of an independent national nuclear deterrent. An enhanced latent nuclear capability that can be operationally deployed on short notice, is both robust and credible, combined with a credible nuclear sharing agreement appear to be sufficient to guarantee Germany security for the time being. A substantial deterioration of the international security environment might change that assessment and associated political-strategic cost-benefit calculus. Whatever moral taboos attach to the making of nuclear policy in the eyes of the general public, German policymakers and planners cannot avoid thinking in greater detail about what Germany is to do in case the US withdraws from NATO.
[1] DGAP, The logic (and grammar) of US grand strategy (Berlin, 2021)
[2] For what it’s worth, some Washington think tanks are increasingly calling for an adjustment of the US global military presence and a restructuring of its security alliances (Cato, Quincy, to name just the most prominent ones).
[3] Nicolas Miller, Stopping the bomb: the sources and effectiveness of US nonproliferation policy (Ithaca, 2018); Alexander Lanoszka, Atomic assurance: the alliance politics of nuclear proliferation (Ithaca, 2018); Mark Trachtenberg, The Cold War and after (Princeton, 2012); Gene Gerzhoy, Alliance coercion and nuclear restraint, International Security 39 (4), 2014
[4] Fred Kaplan, Wizards of Armageddon (Stanford, 1991)
[5] Politico, How Washington own the UK’s nukes, 2015
[6] See footnote 3
[7] Robert Jervis, The meaning of the nuclear revolution (Ithaca, 1989). For a contrarian view, see Keir Lieber, The myth of the nuclear revolution (Ithaca, 2020)
[8] Todd Sechser and Matthew Fuhrmann, Nuclear weapons and coercive diplomacy (Cambridge, 2017); for a critical view of empirical evidence supporting coercion thesis, see Francis Gavin, Nuclear weapons and American grand strategy (Washington DC, 2020)
[9] Matthew Kroenig, The logic of American nuclear strategy (Oxford, 2018)
[10] RAND, Understanding deterrence, Perspective (Santa Monica, 2018)
[11] Robert Art, To what ends military power, International Security (4), 1980
[12] Carnegie, Tracking the German nuclear debate, August 15, 2018 (last updated March 5, 2020)
[13] Scott Sagan, The spread of nuclear weapons (New York, 2003)
[14] “Strategies” include hedging, sprinting, sheltering pursuit, and hiding, see Vipin Narang, Strategies of nuclear proliferation, International Security 41 (3), 2016
[10] RAND, Understanding deterrence, Perspective (Santa Monica, 2018)
[11] Robert Art, To what ends military power, International Security (4), 1980
[12] Carnegie, Tracking the German nuclear debate, August 15, 2018 (last updated March 5, 2020)
[13] Scott Sagan, The spread of nuclear weapons (New York, 2003)
[14] “Strategies” include hedging, sprinting, sheltering pursuit, and hiding, see Vipin Narang, Strategies of nuclear proliferation, International Security 41 (3), 2016