本文系美国CSIS(Center for Strategic & International Studies)发表的一篇报告的简要翻译，略去了前言和附录部分。中文翻译仅作起提示和索引作用，请参照原文：

本文建议美国采取“慎重反应”（Measured Response）核战略，通过研发新武器及前置部署等方式增强战术核力量，以主导在实战中可能出现的核升级，从而达成威慑。


Project Atom: A Competitive Strategies Approach to Defining U.S. Nuclear Strategy and Posture for 2025–2050

Study Objective研究目标

The end of the Cold War and the 9/11 terrorist attacks on the U.S. homeland have profoundly changed the global security environment and reordered U.S. security priorities. During the Cold War, sometimes characterized as “the
first nuclear age,” the United States and the Soviet Union engaged in a nuclear arms race as each side pursued massive nuclear arsenals sized and shaped to fight nuclear wars with each other. Nuclear issues were deemed so important that the U.S. nuclear deterrent
was often characterized as its strategic deterrent,because it was the primary strategy for coping with the existential threat posed by Soviet nuclear weapons. Today, the threat posed to the United States by nuclear-armed nation-states is not even the top-ranked
nuclear danger, as the 2010 Nuclear Posture Review(NPR) report elevated nuclear terrorism and nuclear proliferation as more important challenges. Today, the American policy community pays little attention to U.S. nuclear strategy and posture, as the nuclear
mission itself has become a neglected backwater in the defense establishment and draws attention only when mistakes and scandals occur.


This loss of saliency for U.S. nuclear strategy and capabilities was clearly demonstrated at the end of George W. Bush’s administration when Congress refused to fund the Reliable Replacement Warhead (RRW) despite a last-minute
campaign by the secretaries of Defense and Energy. While the role of nuclear weapons in U.S. security policy has clearly declined since the Cold War, reducing it further did not become official policy until President Obama, in his April 2009 Prague speech,
committed the United States to the long-term pursuit of a world without nuclear weapons. Although President Obama has stated repeatedly (both in his Prague speech and since) that the United States must maintain a“safe, secure, and effective” nuclear force
for “as long as nuclear weapons exist,” he also stated in June 2013 that the United States will never be “truly secure” as long as nuclear weapons exist. Given the presidential-level commitment to reduce the role of nuclear weapons, it is not surprising that
there has been little serious attention, much less national debate, about U.S. nuclear strategy and posture in what Paul Bracken has characterized as “the second nuclear age”—that is, a world in which regional rivalries, sectarian conflicts,and competitions
for resources (to name only a few) occur “in a nuclear context” because they increasingly involve states armed with nuclear weapons. Today, the United States pursues a strategy that is anchored in Cold War concepts and seeks to sustain a smaller version of
the nuclear posture that supported its Cold War strategy. Almost by definition,this is not the right posture for the second nuclear age. Looking ahead to the 2017–2018 NPR process, Project Atom launched a zero-based, “blue sky” review of U.S. nuclear strategy
and force posture that addressed the fundamental issues:

Bracken将现在称作“第二个核时代”，即有核国家间在“核环境”下的地区冲突、宗教冲突和资源冲突。如今，美国核战略基于冷战期间的观念，但是一个“弱化”版本。这显然不是“第二个核时代”中的恰当战略。展望2017-2018核态势报告，Project Atom(即本文)对美国核战略和态势做了“零基础、纯理论”的总结，议题如下：

• What should U.S. nuclear strategy be for the new era, defined as 2025–2050?
• 美国在新时代，即2025-2050间的核战略应该是什么？

• What U.S. nuclear posture is needed to support that strategy?
• 这一战略需要什么样的核态势？

This “clean slate” review was predicated on the assumption that the vision of a world without nuclear weapons is not feasible for the foreseeable future. It was unconstrained by current strategy (e.g., reducing the role of
nuclear weapons in U.S. strategy) and current policy (e.g., the self-imposed prohibition against new nuclear weapons or new nuclear capabilities). However, it was constrained by likely technological trends and the afford ability of nuclear modernization (approximately
$35 billion per year in constant 2013 dollars, comprising 4–5 ­percent of the defense budget). In the effort to generate new thinking about first-order questions, Project Atom followed a competitive strategies approach, which the CSIS study team modified during
its execution.

本文认为无核世界在可预期未来不会实现。它不被当前战略（降低核武器在美国战略中的地位）和政策（对新型核武器和核能力的自缚手脚）约束，但被类似的科技趋势和核武现代化开销（350亿美元/年，以2013年美元计，占军费的4~5%）。Project Atom遵循CSIS研究团队修正后的，竞争性战略方法。

Methodological Approach方法论


Defining the 2025-2050 Security Environment 定义2025-2050安全环境

As defined in the template and framing assumptions paper (see Appendix H), the 2030+ Likely Future is a “projection of current trends and likely developments that takes the current security environment as its departure point
and projects how it evolves in the absence of ‘wild cards,’ discontinuities, ‘black swans,’ and other game-changing events that would significantly change the nature of the 2030+ security environment.” To ensure that think tank team positions were comparable
within a common framework, the CSIS study team relied on an issue template that identified the questions each team had to address and“framing assumptions” (FAs), which were the trends and likely developments that established the boundary conditions for think
tank team analysis. These “framing assumptions”were iterated several times with the working group (Appendix H was version #5). With respect to the 2030+ security environment, the working groups accepted the following out of those proposed in Appendix H:

研究人员最终对2030+的安全环境做出如下假设，下称为《2030+ Likely Future》：

• FA #2: As the world’s strongest (although its margins are decreasing) military power, still with many economic strengths, the United States will continue its post-World War II role as a provider of global stability and principal
architect of the international order.
• 尽管美军的优势正在减少，美国自身面临经济问题，但美国仍将扮演它在二战后的角色：国际稳定的提供者和世界秩序的缔造者。

• FA #3: Nuclear weapons in the twenty-first century are one of several weapons that can have strategic effects on a crisis or conflict.
• Ballistic missile defenses (BMD) will increase the ability to defend against regional small-scale missile attacks but have little utility against nuclear arsenals the size of Russia’s
and China’s.
• Irregular means of delivering a nuclear weapon cannot be entirely eliminated.
• By 2050, the capacity for destruction and disruption of chemical and biological weapons and offensive cyber weapons will have increased significantly, making it necessary to deter and defend against them (although not necessarily
with nuclear weapons).
• Vulnerability of space-based assets will grow, but nuclear weapons will not have been deployed in space and space-based lasers will remain impractical.
• Improving conventional prompt global strike (CPGS) capabilities will increase concern among some, if not all, nuclear-armed powers about the risk of nonnuclear attacks on their nuclear weapons, which (when combined with more
effective BMD) could negate their assured second-strike capability against the United States.
• FA #7: The 2030+ Likely Future will have 9 to 11 nuclear powers.
• While the possible addition of Iran, followed closely by Saudi Arabia, to the nuclear club would complicate and raise the stakes in the already complex, uncertain, and violent Middle East, it would not have the global impact
that more widespread nuclear proliferation would have. A “proliferated world,” defined in this study as a world of 18 nuclear powers (see Appendix H), would fully realize Paul Bracken’s “second nuclear age” since many more regional conflicts would have a nuclear
• 在二十一世纪，核武器是能在危机或冲突中起到战略影响的几种武器之一。
• 弹道导弹防御(BMD)有助于抵抗区域性，小规模导弹打击，但在中/俄的核武库规模面前并无意义。
• 投放核武器的非常规方式无法被彻底消除。
• 到2050年，生化武器的摧毁和破坏能力将显著增加，因此有必要对此进行威慑和防御（尽管对核武器并无可能）。
• 天基设备更加脆弱，但核武器不会在太空部署，天基激光器仍未实战化。
• 增强的全球快速常规打击（CPGS）能力将引起一些（如果不是所有）有核大国对它们核武器遭常规打击风险的关注，和反导相结合，这可能抵消它们面对美国的二次反击能力。
• 在2030+，可能会有9到11个有核国家。
• 伊朗、沙特可能加入核俱乐部，这会进一步恶化中东局势，但对全球的影响不如更广泛的核扩散。一个“核扩散世界”，即有18个有核国家（见附录H
）的世界，将完全实现Paul Bracken的“第二个核时代”，因为区域冲突可能同样与核武器相关联。

A straight-line projection of today’s security environment, particularly if it is only to 2030+, does not force significant changes to today’s U.S. nuclear posture. If the nuclear triad (plus forward-deployed nuclear bombs
in North Atlantic Treaty Organization [NATO] Europe) “works” today, it should work 10–15 years from now. Given the “sunk costs” of prior investment in U.S. nuclear capabilities and the era of austerity triggered by the Budget Control Act of 2011, the overriding
bureaucratic and fiscal imperative to extend the life of current systems as long as possible (e.g., a recent RAND study envisions incremental life-extension actions for Minuteman III for decades beyond initial projections). Nuclear warheads wear out (see the
B61 bomb), as do delivery systems (see the air-launched cruise missile [ALCM] and Ohio-class submarine), and will need to be replaced, but the fiscal environment will suppress the pace of U.S. nuclear modernization. The United States could afford to spend
more on its nuclear capabilities—even the largest estimate of a trillion dollars over 30 years still comprises less than 5 ­percent of the overall defense budget—but is unlikely to unless the security environment changes markedly and significantly increases
the perceived role and value of U.S. nuclear weapons in its security strategy.


There is no neatly empirical way to think about nuclear weapons or about the future. Blast radius, heat, fragmentation, and radiation levels can be calculated. Allied and adversary perception cannot—not
tomorrow, and certainly not 30 years in the future. To think about the future need for nuclear weapons requires no small degree of imagination. To make policy choices—
which must be made—requires
judgment based on that imagination.


When it comes to nuclear weapons, there is little that historical precedent or experience can provide. There has never been a nuclear exchange between nations. The only use of atomic weapons, by the
United States against Japan on 6 and 9 August 1945, yields little insight about what would happen if nuclear weapons were employed during a war. Even
 the conclusion that nuclear weapons ended World War II by breaking the Japanese
will to fight is still being debated.
 This is also the case with the non-use of nuclear weapons (the so-called nuclear taboo) and the theory and practice of deterrence during the Cold War. Did
it work or were the Cold War opponents lucky?


My views on the nature of the 2025–2050 security environment are considerably more pessimistic than those expressed in the 2030+ Likely Future. The
recommendations made here are based on two related propositions about what would occur
in the absenceof an effective U.S. nuclear strategy to counteract these trends. Of course, these propositions
judgments, not absolute truths, and are debatable. They also risk being self-fulflling prophecies, because strategies and weapons designed to cope with a more threatening security environment often make it more likely that the darker future will,
indeed, occur. However, that risk is outweighed by the risk of planning for a more benign future and being unprepared for the grimmer one that the United States might actually face. While acknowledging up front that two propositions
below are debatable, they are made explicitly in order to facilitate a debate on the fundamentals, which is consistent with the competitive strategies approach of Project Atom.

我对2025-2050年安全环境的预测比《2030+ Likely Future》中悲观得多。这里的建议基于两个相关命题，关于如果美国核战略未能有效阻止这些趋势，将会发生什么。当然，这些命题只是判断，而非事实。但它们也可能成为“自我实现的预言”，因为针对更危险局势的战略和武器自身可能造成黑暗的未来。但这种风险比乐观预计未来，并对危险毫无准备要好得多。如果承认下面两个命题是可争论的，它们的表达方式十分利于争论其基础，这与Project Atom中所描述的”竞争型战略”一致。

Proposition #1: The dynamics of the 2025–2050 security environment will cause further nuclear proliferation—perhaps not to the 18 nuclear powers envisioned in an alternative future, but higher
than the 9-to-11 nuclear powers of the 2030
+Likely Future.
命题1：2025-2050年间的安全环境变化将导致进一步的核扩散——或许不会有18个拥核国，但比《2030+ Likely Future》中预言的9~11个拥核国要多。

Proliferation optimists note that warnings over the coming cascade of proliferation have been made for decades, most notably by President John F. kennedy, but have not materialized. However, the current
trend line is quite negative:


• The United States invaded Iraq in 2003 in large part because the Bush administration wanted to prevent Saddam Hussein from getting nuclear weapons; Hussein was rapidly
removed from power and subsequently hanged in a Baghdad basement.
• Perhaps startled by the ease with which the United States removed Hussein from power, Muammar el-Qaddaf gave up his nuclear weapons program and ended up dying even more ignominiously than his Iraqi
• Despite receiving several “red-line” warnings and becoming more isolated, both diplomatically and economically, North korea joined the nuclear club even as the Kim dynasty endured a generational change
of power; in this instance, acquiring a nuclear weapon has helped ensure regime survival.
• The jury is out on whether Iran will give up its nuclear weapons program, but many believe that Saudi Arabia would rapidly “go nuclear” if Iran joined the Democratic People’s Republic of Korea (DPRK)
as the newest members of the nuclear club;
• With three Middle Eastern powers in the nuclear fold, the incentives would grow for Egypt and Turkey to follow suit.
• If such a regional proliferation cascade occurred, the perceived power of the United States would be diminished, which would have repercussions elsewhere as regional allies increasingly doubt the will and ability of the United States to counter a more belligerent
Russia and an increasingly assertive China.

• 美国在2003年侵略伊拉克，很大程度因为布什政府希望组织萨达姆拥有核武器；萨达姆很快被剥夺权力并被绞死。
• 或许出于伊拉克战争带来的震撼，卡扎菲放弃了核武器，最终比萨达姆死得更惨。
• 北朝鲜甚至在政权更迭之际加入“核俱乐部”，尽管虽然得到了许多“红线”警告，并被从外交和经济上孤立。在这个例子中，拥核保证了其政权的延续。
• 对伊朗是否放弃核计划尚无定论，但许多人相信如果伊朗效仿朝鲜加入“核俱乐部”，沙特将紧随其后拥核。
• 在三个中东强国拥核后，埃及和土耳其亦会有拥核的动机。
• 如果此种核武器的“滑坡式扩散”发生，世界将认为美国的力量衰退，这将让其他地方的美国盟友怀疑美国还击更加好斗的俄罗斯，和愈发专断的中国的决心与能力。

A major stimulus for a faster rate of nuclear proliferation is U.S. conventional military superiority. This causes nonnuclear nation-states (such as North Korea, Iran, Iraq, Syria, and Libya) to pursue
nuclear weapons as a counter or offset to U.S. military prowess. It also leads nuclear-armed states with interests in opposition to the United States (Russia, for sure, and perhaps China) to increase their reliance on nuclear weapons, much in the way
that the United States did during the Cold War.
 Although the margin of U.S. conventional superiority has never been as great as often proclaimed (e.g., see the lower end of the spectrum of conﬂict)
and is declining relative to other major powers, the prospect of a conventional-only war with the United States is a losing proposition for any state. The value of nuclear weapons as a “trump card” for negating U.S. conventional power was enhanced by the U.S.
invasion of Iraq in 2003 to prevent Saddam Hussein from acquiring a nuclear weapon. If the United States apparently believes that it can be deterred by an adversary’s nuclear weapons, why would a nonnuclear “regional rogue” not want one? This leads directly
to my second (more pessimistic) proposition about the 2025–2050 security environment:


Proposition #2: The credibility of U.S. extended nuclear deterrence, as well as the assurance that U.S. allies and friends derive from it, will decline significantly in 2025–2050, in part because
of the failure to prevent further nuclear proliferation。


More nuclear-­armed regional adversaries (to the United States and its allies) and increased reliance on nuclear weapons by major powers in competition with the United States will lead U.S. nonnuclear allies to rely more on
U.S. security commitments, especially with regard to extended nuclear deterrence. However, the credibility of those commitments will have been weakened by the failure of U.S.-­led efforts to prevent the nuclear
proliferation that led to the increased demand from its allies for help in deterring nuclear-­armed adversaries. While some (including myself) argue that it is not realistic to believe that a nation both capable of acquiring a nuclear weapon and determined
to do so can be stopped, the inability of the United States to prevent what it has repeatedly declared is “unacceptable” will erode its credibility to cope with the “unacceptable” when it nevertheless happens.


U.S. threats to employ the full range of its military capabilities (including nuclear weapons) to respond to nuclear attacks against their allies are at the core of both extended deterrence and assurance. How credible those
“statements of intent” are to potential adversaries (in the case of extended deterrence) and to its allies (in the case of assurance) depend on adversarial and allied perceptions of U.S. nuclear capabilities and will:


• As reflected in the now-­infamous Healey theorem, which states that credible assurance requires a 95 ­percent probability that a nuclear threat will be carried out versus a 5 ­percent probability for credible deterrence,
the standards for credibility will depend on context and the specific actors. 
• How credible will U.S. security commitments be in 2025–2050, both to its adversaries and its allies? ­After North Korea’s nuclear test in February 2013 and statements by the United States that it would not consider redeploying tactical nuclear weapons (TNWs)
on the peninsula, 66 ­percent (10 percentage points higher than in 2010) of the South Korean public supported a domestic nuclear weapons program. 
• Assurance in 2025–2050 will depend less on what the United States says to its allies about its commitment to them and more on the allies’ perception of how well the United States actually acts when its security commitments are challenged. Today, the United
States and its allies are “talking the talk,” but that is less likely to be enough in the ­future.
• As demonstrated recently with res­pect to U.S. enforcement of red lines against the use of chemical weapons in Syria, credibility can be lost, and once lost, may be hard to reestablish. Nuclear-­armed regional powers, many with irredentist agendas, will engage
in more provocative be­hav­ior (see North ­Korea in 2010) and erode the faith of U.S. allies in U.S. ­extended deterrence commitments.
• In a 2006 study (in which I participated) on realigning the U.S. global military posture, a se­nior South Korean defense official, when asked about the U.S. willingness to risk San Francisco for Seoul, said, “I think I believe it, but I’m not sure the Chinese

• 根据臭名昭著的“Healey Theorem”：让盟友放心需要95%的核威慑可信度，而威慑敌人只需要5%，可信度的标准取决于环境和对象。
• 2025-2050年间，美国的安全承诺对其盟友和敌人有多可信？在2013年二月朝鲜核试验，并且美国宣称不会在朝鲜半岛部署战术核武器后，66%的韩国人（比2010年多10%）支持韩国研制核武器。
• 2025-2050年间，盟友对自身安全的信心将更多来自它们对美国实际行为的认知，而非空洞的安全承诺。如今美国和盟友谈笑风生，但这对未来远远不够。
• 正如美国执行对叙利亚核武“红线”中暴露的那样，信任一旦丧失就难以重建。有核地区大国——许多都有民族诉求——将愈发挑衅（例如2010年的朝鲜），并侵蚀美国盟友对其核保护伞的信任。
• 在2006年关于重组美军全球态势的一项研究中，一位韩国高级官员在被问道是否相信美国将用旧金山交换首尔时说，“我觉得我相信，但我不确定中国会相信这个。”

A faster rate of nuclear proliferation both adds to the demand for the U.S. nuclear umbrella and erodes its credibility. This vicious circle is likely to continue unless the United States moves forcefully to counter it, which,
in my judgment, requires a U.S. nuclear strategy designed for twenty-first century realities. Adoption of the recommended strategy could limited nuclear proliferation to the greater Middle east and prevent it from spreading to Northeast Asia, Europe, and elsewhere.


2025–2050: The Role or Function of U.S. Nuclear Weapons 美国核武器的角色

The principal role of U.S. nuclear weapons is to deter other states from employing nuclear weapons against the United States and its allies. U.S. nuclear weapons ensure that any major conﬂict with the United States has a nuclear
dimension and occurs under a “nuclear shadow.” Deterring nuclear attacks is not the sole purpose of U.S. nuclear weapons, in part because it is U.S. policy to maintain “strategic ambiguity” about the circumstances under which the United States might actually
employ nuclear weapons. In perhaps the last semi-explicit nuclear threat made by the United States, Secretary of State Jim Baker told Tariq Aziz, Iraq’s foreign minister, that “If you use chemical or biological weapons against U.S. forces, the American people
will demand vengeance. And we have the means to exact it . . . This is not a threat, it is a promise.” Although the effect of this implied threat of nuclear retaliation on Iraq’s behavior is still the subject of much debate, the possession of nuclear weapons
by the United States (and any other nuclear-armed state, for that matter) has an inherent or intrinsic deterrent effect, because it, unlike nonnuclear states, can escalate to the nuclear level. 

美国核武器扮演的主要角色是防止其他国家对美国或其盟友使用核武器。美国的核武器保障了任何同美国的大规模冲突都处在“核阴影”之下。防止核攻击不是美国核武器的唯一目的，部分处于美国对在何种情况下将使用核武器采取刻意的暧昧政策。或许美国上次“半正式”的核威胁是国务卿吉姆·贝克对伊拉克外交部长Tariq Aziz所说的：“如果你们对美军运用生化武器，美国人民将要求复仇。我们有能力实现它——这不是威胁，这是承诺。”虽然这种隐含的核报复威胁所造成的影响仍处争论中，一个拥有核武器的美国（当然还包括其他国家）有一种内在的威慑效果，因为与无核国家不同，它可以将冲突升级至核层面。

• Debates over declaratory policies such as no-first-use have always been a little unreal. The circumstances under which a state—that is, the men and women acting on behalf of that nation—would actually employ a nuclear weapon
are characterized by extreme urgency, great peril, and fundamental uncertainty. Statements made during peacetime about what a nation’s leadership would actually do under those circumstances have always been speculative, if only, as Yogi Berra is alleged to
have said, “making predictions is awfully hard, particularly about the future.”

• 例如“不首先使用核武器”这样的公开政策总显得不太现实。国家决策层做出核打击决策的环境是高度急迫，危险切不确定的。在这种情况下，和平时期的声明仅有推测作用，正如尤吉·贝拉（著名棒球运动员）所说，“做预测极度困难，特别是预测未来。”

Nuclear weapons are a critical element of the global distribution of power that provides the underlying structure for relationships (including deterrence) among all states, not just those states seeking to oppose the United
States. The world is divided into nuclear-armed and nonnuclear states, the latter of which includes “threshold nuclear powers” or “latent nuclear powers” (i.e., states that could “go nuclear” fairly quickly) and “nuclear wannabes” (a group that used to include
North Korea). How U.S. nuclear capabilities stack up against those of other nuclear-armed states matters. Since World War II, the U.S. superpower status has included maintaining nuclear capabilities that are “second-to-none,” which, as will be discussed, the
United States should sustain in 2025–2050.


2025–2050: Recommended U.S. Nuclear Strategy 建议的美国核战略


The scenarios for nuclear employment have changed greatly since the “balance of terror” between the two global superpowers. During “the first nuclear age,” it was the mutual fear of nuclear escalation that kept the Cold War
cold as the United States and the Soviet Union engaged in Thomas Schelling’s “competition in risk taking.” In “the second nuclear age, our adversaries have to cope with a United States that both possesses conventional superiority and acts as if nuclear war
were unthinkable. Of course, they are thinking through how they might actually employ a nuclear weapon to get the United States to “back off” in a crisis or conﬂict. Russian military officers have said they are developing “very low-yield” weapons (most likely
in the sub-kiloton range) that will be very accurate and “clean” (i.e., producing little radiation), thus minimizing collateral damage. If such a weapon were employed against U.S. or allied forces, the United States might not “respond in kind,” because its
nuclear response options were larger, “dirtier,” and caused significant collateral damage. To counter this risk of “self-deterrence,” the United States needs more discriminate nuclear options across the range of nuclear attacks.

核武器的运用场景自美苏“恐怖平衡”以来发生了巨大改变。在“第一个核时代”，双方对核升级的恐惧阻止了冷战变热，导致美苏陷入Thomas Schelling所说的“对承受危险能力的竞赛”。在“第二个核时代”，我们的对手必须面对美国的常规军力优势，同时核战争仍然无法想象。当然，他们仍在设想如何在使用核武器的同时令美国“服软”。俄罗斯军官称，他们部署了既精确又“清洁”（辐射极少）的极低当量核武器（大致不超过千吨级），从而最小化连带损伤。如果这种武器被用来对付美国或盟友的军队，美国很可能不会进行对等报复，因为其核报复的范围更大，更“脏”，并会造成大量连带损伤。为了反对“自我威慑”的风险，美国需要对各种层面核打击更有区分度的核报复选择。

The United States is not well postured for this type of nuclear employment scenario. Its Cold War-era nuclear weapons were designed for a global conﬂict involving thousands of high-yield weapons in a massive exchange. The United States needs to develop and
deploy more employable nuclear weapons, ones that enable the United States to respond directly and proportionately to an adversary’s employment of a nuclear weapon. This is not about “nuclear war-fighting,” but demonstrating the resolve to match an adversary’s
escalation of a conﬂict to the nuclear level. By doing so, the United States sends a powerful political message—“You can’t win this conﬂict by going nuclear”—and, in effect, makes nuclear escalation a less attractive option.


Credibility, it is often noted, is always in the eyes of the beholder. To a potential adversary considering employing a nuclear weapon to offset the conventional superiority of the United States, the awareness that the United
States has anticipated this eventuality and developed more discriminate, more employable nuclear options of its own will be doubly impactful, because it demonstrates the same kind of hard-nosed, realistic thinking that led him to consider employing a nuclear
weapon in the first place.


The Stimson Center paper notes that their recommended nuclear posture is “dependent on U.S. conventional military superiority” and “so does not need to rely on weak state
tactics.” This misses the basic point—the United States needs to focus on its nuclear deterrent because its potential adversaries will rely more on nuclear capabilities to compensate for their conventional weakness. U.S. conventional superiority gives it escalation
control at the conventional level and causes its adversaries to think about breaking the nuclear threshold. The United States needs employable nuclear options at all rungs of the nuclear escalation ladder to make that option unattractive as well.

Stimson Center的论文提及，他们建议的核态势依靠美国的常规军力优势，因此不需要依赖弱国的策略。这忽略了重点——美国需要关注核威慑，因为其潜在对手将更加依赖核能力去弥补常规劣势。美国的常规优势赋予它在常规层面的“升级控制”，并导致其对手设想突破“核门槛”。美国在核升级的各个等级都需要可运用的核武器，从而使核升级不再具有吸引力。


With the exception of about 200 B61 nuclear bombs deployed in five NATO Europe countries, the United States no longer forward deploys nonstrategic nuclear forces (NSNF). U.S. naval surface ships no longer carry nuclear weapons
and the nuclear variant of the U.S. Navy’s cruise missile (TLAM-N), which was once characterized as the Navy’s “theater nuclear weapon” to be used in defense of its Northeast Asian allies, has been withdrawn from service. The United States still forward deploys
American military personnel (albeit in much lower numbers) but has largely dismantled the “inner ring” of nuclear weapons that once encircled its principal adversaries.


U.S.-extended deterrence commitments will be significantly less credible (both to potential adversaries and our allies) in 2025–2050 than they are today unless that commitment is provided by U.S. nuclear weapons based on the
territory of the ally whose security is threatened by a nuclear-armed regional adversary. Extended deterrent threats are inherently less believable than direct deterrence threats, since they involve putting the U.S. homeland at risk by attacking the adversary’s
homeland in response to a nuclear attack on the homeland of the U.S. ally. This dilemma is often expressed in the question “Will the United States trade Los Angeles (or New York City) for Tokyo (or Berlin)?”


How Russia is thinking about its nuclear weapons: at the level of doctrine 俄罗斯如何看待核武器：政策层面

In his masterful survey of the emerging nuclear landscape, Paul I. Bernstein concludes: “[It] is clear that Russia’s nuclear strategy today encompasses a concept for deterring
and terminating conventional war based on the threat of limited nuclear strikes for the purposes of “demonstration” and “de-escalation.” In this context, these terms refer to a “limited counter-force nuclear strike in the theater of military operations”—an
action compensating for conventional force weakness intended to compel the adversary’s withdrawal by signaling Russia’s high stake in the conﬂict and its willingness to escalate the level of violence in order to prevail. This approach, premised as it is on
the strategy of nuclear first use against a conventionally superior adversary to alter the political dynamics of conﬂict, is strikingly similar to the concept of ﬂexible response that defined NATO’s strategy for many years.”
在关于核形势的研究中，Paul I.Bernstein总结道：“如今的俄罗斯核战略包括通过有限核打击进行‘示威’和‘降级’，从而拒止和终止常规战争。其中“有限核报复”弥补了常规军力的不足，宣示了俄罗斯通过将冲突升级至核层面而获胜的意愿，从而迫使敌人撤退。这种对常规优势敌人首先使用核武器的战略和北约多年来的‘灵活反应’战略类似。”
—Paul I. Bernstein, “The Emerging Nuclear Landscape,” in On Limited Nuclear War in the 21st Century, ed. Jeffrey A. Larsen and Kerry M. Kartchner (Stanford, CA: Stanford
Security Studies, 2014), 109. 

“Coupling” U.S. security to the security of its allies was always a huge challenge during the Cold War. Although U.S. nuclear strategy and employment policy changed from “massive
retaliation” to ﬂexible response, it was the presence of 7,000 U.S. nuclear weapons in Europe that ensured that any major conﬂict in the Europe region would escalate rapidly to nuclear war. And the United States deployed hundreds of nuclear weapons in South
Korea (and about 3,000 nonstrategic nuclear weapons in the Pacific Region) to underscore its extended deterrence there. This encirclement by forward-based U.S. nuclear weapons worked during the Cold War and was largely dismantled after the Cold War ended.


In 2025–2050, the goals of U.S. nuclear strategy will remain the same, but the manner in which they are pursued will likely change. The 2014 Quadrennial Defense Report (QDR) states that

Our nuclear deterrent is the ultimate protection against a nuclear attack on the United States, and through extended nuclear deterrence, it also serves to reassure our distant allies of their security against regional aggression.
It also supports our ability to project power by communicating to potential nuclear-armed adversaries that they cannot escalate their way out of failed conventional aggression。

When security anxieties are acute, “reassurance” or “assurance” is most reliably provided by credible extended deterrence—if American allies’ adversaries are deterred, they
will be assured. Deterring regional adversaries from “going nuclear” requires credible nuclear responses to their nuclear attack options. Forward deploying a robust set of discriminate nuclear response options conveys the message that the United States will “respond
in kind” and proportionately to nuclear attacks upon its allies. The credibility of that message is reinforced because the U.S. homeland would not be engaged in the U.S. response to a nuclear attack on a regional ally, which leaves the burden on the regional aggressor
to escalate to the level of “homeland exchanges.” The price, however, for this more credible U.S. “nuclear umbrella,” is the ally’s willingness to host U.S. nuclear weapons.  This is what constitutes “nuclear burden sharing” in 2025–2050.


How Russia is thinking about its nuclear weapons: in messaging NATO 俄罗斯如何看待核武器：向北约传递信息

In a recent policy brief on “close military encounters”—defined as violations of national airspace, emergency scrambles, narrowly avoided mid-air collisions, close encounters
at sea, and other dangerous actions”—between Russia and the West, a European Leadership Network (ELN) brief noted that NATO had already conducted over 100 intercepts of Russian aircraft by late October 2014, three times more than in 2013. The brief identified
and categorized three types of incidents: 2 High Risk (a high probability of casualties or direct military confrontation) ones; 11 Serious Incidents with Escalation Risk; and 15n Near Routine Incidents, whose growing frequency added to “an atmosphere of tension.”
The ELN policy brief also noted that “Russia has also been conducting a series of major exercises involving various units from the Western and Southern Military Districts. The geographical extent of these exercises ranges from the Black Sea littoral through
the Russian border with Ukraine, and involves units from not only the Army, Navy, and Air Forces, but also from Russia’s Strategic Nuclear Forces. These activities . . . have been rightly perceived as threatening actions by Russia’s neighbors.”


—Thomas Frear, Łukasz Kulesa, and Ian Kearns, “Dangerous Brinkmanship: Close Military Encounters Between Russia and the West in 2014,” (London: European Leadership Network,
November 2014), 9.

How Russia is thinking about its nuclear weapon: heavy handed diplomacy 俄罗斯如何看待核武器：强硬外交

“I want to remind you that Russia is one of the most powerful nuclear nations. This is a reality, not just words . . . [other countries] should understand it’s best not
to mess with us.” — Vladimir Putin, August 29, 2014
“We hope that our partners will realize the recklessness of attempts to blackmail Russia, will remember the risks that a spat between major nuclear powers incurs for strategic
stability.” — Vladimir Putin, October 15, 2014
“You can do a lot more with weapons and politeness than just politeness.” — Vladimir Putin, November 19, 2014
“Sometimes I think, maybe it would be better for our bear to sit quiet, rather than chasing around the forest for piglets. To sit eating berries and honey instead. Maybe they will leave it in peace. They will not. Because they will always try to put him on
a chain, and as soon as they succeed in doing so they tear out his fangs and claws. [By “fangs and claws,” Putin said he meant Russia’s nuclear weapons.] Once they’ve taken out his claws and fangs, then the bear is no longer necessary. He’ll become a stuffed
animal. The issue is not Crimea, the issue is that we are protecting our sovereignty and our right to exist.”—Vladimir Putin, December 18, 2014


Some U.S. allies will be tempted to get their nuclear deterrence “on the cheap.” Preferring to remain a nonnuclear state and unwilling to host U.S. nuclear weapons, they will do the “assurance dance” and press the United States
to bolster the credibility of its extended deterrent by adopting a “stronger” declaratory policy, engaging in more intensive alliance consultations, and the like. This may “work” today but is increasingly less likely to in the more perilous security environment
of 2025-2050. “On the cheap” extended deterrence in the twenty-first century will be less credible, if only because it requires that the United States accept a disproportionate share of the risks associated with nuclear deterrence.


In regions containing a nuclear-armed aggressor, the choices facing nonnuclear states are likely to be increasingly stark: acquire one’s own nuclear weapons, host nuclear weapons from a non-regional actor (and pay the price
of alignment), or accommodate the regional aggressor (by appeasement, realignment, etc.). The post-Cold War era seems to be coming to an end; the realities of the “post-post-Cold War era” will be harsher and the trade-offs will be clearer to all, including
allied and American publics.


The nuclear strategy being recommended here is called “Measured Response.” This is not a new strategy——it is grounded in the U.S. strategy of escalation control that evolved as the United States adopted its flexible response
strategy in the 1960s. As Kerry M. Kartchner and Michael S. Gerson observe:

我们建议的核战略叫“慎重反应”。这不是新战略——它基于1960年代“灵活反应战略”中的控制升级。正如Kerry M, Kartchner和Michale S.Gerson观察到的：

The underlying logic of escalation control originated in the Kennedy administration, when Secretary of Defense Robert McNamara shifted U.S. nuclear war plans away from a single, all-out nuclear attack against the full range
of military, economic, and civilian targets in Warsaw Pact countries, to a strategy that emphasized initial strikes only on Soviet nuclear forces. The central idea was that, rather than using its forces all at once, the United States would first execute a
more limited strike and use its remaining weapons to deter Soviet escalation by threatening additional attacks. . . . The combination of smaller, controlled nuclear strikes and a large, survivable reserve force that would be used to threaten further attacks
was at the heart
of strategies for escalation control. Subsequent revisions to U.S. nuclear war plans, especially in the Nixon and Carter administrations, were intended to provide increasingly limited and flexible nuclear options to enhance the credibility of deterrence and,
if deterrence failed, to control escalation and terminate the war at the lowest possible level of violence.


Russia’s growing reliance on nuclear weapons has led it to plan for and exercise the early employment of a nuclear weapon in a conflict with a superior conventional foe. China is modernizing and expanding its nuclear forces,
in part to ensure their survivability against the combination of U.S. advanced conventional weapons and improving ballistic missiles defenses. Despite the veil of opaqueness on any Chinese thinking about how it might employ its nuclear weapons against the
United States, I have little doubt that they are. The United States needs to think about how to counter that.


However, this is not a strategy of “escalation dominance,” which was defined by Kartchner and Gerson as the ability “to fight harder, longer, and more effectively than the Soviets at all levels of conflict short of general
nuclear war,” a capability that, in effect, required nuclear superiority. Deterring an adversary from breaking the nuclear threshold is not the same as preparing for limited nuclear war. It’s about ensuring that there are no gaps in U.S. nuclear response options
that would prevent it from retaliating proportionately to any employment of a nuclear weapon against the United States and its allies. If unable to respond proportionately, the United States could be “self-deterred,” because responding in kind (i.e., with
a nuclear weapon) might be seen (by American decisionmakers) as going “too far” up the escalatory ladder.


U.S. conventional superiority lowers the nuclear threshold, because it tempts conventionally weaker adversaries to early (rather than as a last resort) employment in order to avoid adverse results at the conventional level.
By having a robust set of proportionate nuclear responses, the United States raises the nuclear threshold because it reduces the attractiveness of nuclear escalation. This may seem paradoxical, to be sure, but paradoxes seem to be endemic to any nuclear era.


While the United States should continue to maintain “strategic ambiguity” about the universe of circumstances that could lead it to employ a nuclear weapon, it should be absolutely clear that it will respond in kind to any
nuclear attack. Failing to do so, even when there might be a nonnuclear response capable of achieving the same military effects (minus the radiation) weakens the U.S. nuclear deterrent, both with the perpetrator of the attack and any other state trying to
assess U.S. willingness to cross the nuclear threshold. There should be no ambiguity about this contingency——”nuke us and we’ll nuke you.” It is Deterrence 101.


2025-2050: Recommended U.S. Nuclear Posture 建议的美国核态势

Before identifying the nuclear weapons—that is, the nuclear warheads and delivery systems—that the United States will need to execute this strategy, this list of ancillary assumptions about supporting capabilities and boundary
conditions needs to be enumerated, because they (in addition to the right nuclear capabilities) are also necessary if the proposed strategy is to succeed:


• Responsive infrastructure. A healthy nuclear complex capable of supporting the recommended posture.
• Robust Nuclear Command and Control (NC2) System. Conducting a limited, tightly controlled nuclear exchange would stress the NC2 system, which would have to be fully effective and resilient.
• Advanced conventional weapons, cyber-and electronic-warfare capabilities could significantly degrade the U.S. ability to conduct controlled nuclear operations,
but the assumption here is that DoD will make the investments needed to cope with them.
• Affordable Nuclear Modernization Program. DoD and Department of Energy (DoE) spending on nuclear weapons remains roughly at current levels—that
is, $30–35 billion per year (in 2015 dollars), about 4–5 percent of the overall defense budget.
• Improved, but not fail-proof, defenses against small-scale nuclear attacks. Effective defenses—against ballistic and cruises missiles, anti-aircraft and unconventional delivery means (e.g., smuggled into CONUS in a ship container)—would raise the barrier
for conducting a nuclear attack against the United States, but would not cancel the threat. The United States remains vulnerable to large-scale nuclear attacks.
• A revitalized nuclear mission in DoD. In adopting the recommended strategy of Escalation Control, the DoD successfully addresses the drift and malaise that characterized the nuclear enterprise in 2007–2014. There is no point in developing and acquiring more
employable nuclear weapons unless the DoD has trained and exercised with them and is seen as willing and able to employ them. 
• As recommended in the author’s March 2008 report on DoD and the Nuclear Mission, this could involve creating a U.S. Nuclear Operations Command modeled
after the U.S. Special Operations Command.

• 相应的基础设施。我们推荐的核态势需要健康的核设施。
• 健壮的核指挥控制（NC2）系统。有限的，严密受控的核交火对NC2系统施加重大压力，它需要时刻保持效率和弹性。
• 敌人先进的常规武器，网络和电子战能力会显著降低美国执行受控核战争的能力，但我们在这里假设国防部会进行必要的投资以应对它们。
• 可负担的核武器现代化方案。国防部和能源部在核武器上的支出大致和现在相同，即300-350亿美元（2015年），约占全部军费的4~5%。
• 改进对小规模核袭击的防备，但并非万无一失。对弹道/巡航导弹，飞机和非传统投送手段（例如装在集装箱里走私）的防御将在核袭击面前筑起更高的栅栏，但不能彻底消灭威胁。美国在大规模核打击面前依然脆弱。
• 国防部复活核任务。通过接受控制升级的战略，国防部能够成功消除2007到2014年核计划带来的偏移和不适。如果国防部不习惯，不愿使用它们，那研发和获取更多可部署核武器毫无意义。
• 正如作者在2008年三月对国防部和核任务做的报告中推荐的那样，这涉及到仿照美国特种作战司令部的形式创建美国核战司令部。

These assumptions are not self-fulfilling and are not trivial. But if the U.S. government fails to make these assumptions come true, the recommended 2025–2050 nuclear strategy and posture will lose much of its effectiveness
and credibility.



The “second-to-none” yardstick for measuring rough parity with Russian nuclear forces does okay at the strategic level: despite Russia’s robust nuclear modernization program, most (but hardly all) U.S. analysts believe that
U.S. strategic nuclear forces meet the “second-to-none” standard for maintaining rough parity with Russia. Russia’s nuclear forces will be considerably younger than that of the United States and will include systems (e.g., road-and rail-mobile intercontinental
ballistic missiles [ICBMs]) not in the U.S. arsenal. But the U.S. nuclear triad of submarine-launched ballistic missiles (SLBMs), ICBMs, and
bombers is sufficiently strong and flexible that few analysts believe that the United States has inferior strategic nuclear forces. Plus, the U.S. nuclear triad is being modernized, albeit at a significantly slower pace than Russia’s.


That is not the case with nonstrategic nuclear weapons (aka “tactical nuclear weapons”)—the United States has one system, the B61 bomb, in its inventory, while Russia retains the full range of its battlefield nuclear weapons
and is modernizing them (e.g., the new Russian Iskander-M is said to be nuclear capable and has been used in exercises involving strategic nuclear forces). The issue is not whether the Russians are superior in this dimension of nuclear weapons; the issue is
whether that superiority matters. While I do not believe that the United States needs to match Russia quantitatively, I do believe that Russia’s qualitative superiority in nonstrategic nuclear weapons does undercut the proposed Measured Response strategy.


Table 1. Warhead yields 表格1：战斗部当量
Designation Warhead Yield (Kilotons)

B-29 Superfortress超级堡垒 Little Boy 15
B-29 Superfortress超级堡垒 Fat Man 21
Current Inventory

ICBM–LGM-30G Minuteman III民兵3 Mk-12A 335
ICBM–LGM-30G Minuteman III民兵3 Mk-21/SERV 300
SLBM–UGM-1323A Trident II D5三叉戟2 Mk-4: 4 W76 MIRV 100
SLBM–UGM-1323A Trident II D5三叉戟2 Mk-4A: 4 W76-1 MIRV 100
SLBM–UGM-1323A Trident II D5三叉戟2 Mk-5: 4 W88 MIRV 455
B-52H Stratofortress同温层堡垒 ALCM: W80-1 5-150
B-2A Spirit幽灵 B61-7/B61-11, B83-1 10-360/400, low-1,200
Nonstrategic–F-16 DCA, F-15E, Tornado B61-3/B61-4 0.3-170/0.3-50

F-15E, F-16 DCA, Tornado, F-35A B61-12 0.3-50

Massive Ordnance Penetrator (MOP)—carried aboard B-2A and B-52H GBU-57A/B 0.003


SERV=Safety Enhanced Reentry Vehicle安全增强型再入载具
MIRV=Multiple Independently Targetable Reentry Vehicle多目标再入载具（即分导多弹头）
ALCM=Air-Launched Cruise Missile空射巡航导弹
Massive Ordnance Penetrator巨型钻地弹，即GBU-57A/B

As illustrated in Table 1, there are several potentially significant “gaps” in U.S. nuclear response options. ICBM warheads are three times as powerful as those carried by Ohio-class submarines, but, at 100 kts, the W-76 is
hardly a discriminatory weapon and is 20 times more powerful than the 5 kt version of the ALCM-delivered W-80 warhead, which is the lowest-yield weapon in the strategic stockpile. As a point of comparison, the 15 kt weapon that incinerated Hiroshima was about
twice (2.08) as powerful as the 5 kt variant of the W-80 warhead on an ALCM. These weapons were designed for the Cold War threat posed by the Soviet Union, which had an inventory that included weapons even larger than the American ones. These weapons are not
very relevant to the nuclear employment scenarios that are likely in 2025–2050.


At the nonstrategic level, the United States does have subkiloton options in the “dial-a-yield” B61-3/4 bomb deployed on dual-capable F-16s. While the smallest variant of the B61 bomb is “only” 0.3 kt, that is still 20 times
(21.5) more powerful than the largest-yield conventional weapon (the 30,000-pound Massive Ordnance Penetrator [MOP]). The B61-3/4 is slated to be replaced by the B61-12, which is also a variable-yield weapon with options that are not yet known (or perhaps
to be determined). If current nuclear modernization plans hold firm, they will be delivered initially by the B-2A and then by the new long-range bomber (LRS-B) and dual-capable F-35As. The “life-extension” program for the B61 bomb will likely result in a weapon
that has at least 2-kiloton-or-smaller variations, but aside from greater accuracy, no additional “special effects” such as enhanced-radiation, earth-penetration, or low-radiation, all of which appear to be in active development in Russia (and elsewhere).
Moreover, unlike their counterparts elsewhere, the U.S. military (with the likely exception of a few cells of planners sprinkled throughout DoD) are not seriously engaged in thinking through (by war-gaming, simulations, etc.) how nuclear weapons might be employed,
much less training and exercising U.S. forces in their employment. The United States is simply not preparing to counter how its potential adversaries are (or may be) preparing to counter its conventional superiority.


The nuclear posture needed for the recommended strategy of Measured Response is quite similar to that recommended by the CNAS think tank team:
我们推荐的“慎重反应”战略所需的核态势同CNAS（Center for a New American Security）智库所推荐的类似：

The ideal U.S. nuclear force is one that is not only highly survivable and able to issue a devastating blow against any adversary under any scenario but that is also capable of conducting limited nuclear operations in a controlled
fashion while maintaining the ability to escalate to full-scale war if necessary. It is a force that can achieve reasonably precise effects . . . under a wide spectrum of possible scenarios, enabling a more effective limited nuclear war capability and thus
providing greater leverage and advantage for the United States.


A robust set of discriminate nuclear warheads deliverable by ballistic missiles, cruise missiles, and aircraft would ensure that the United States could respond in kind and proportionately to any nuclear attack against the
United States and its allies. Special-effects weapons include low collateral, enhanced radiation, earth penetration, electromagnetic pulse, and others to be determined (as technology advances and the renewed nuclear enterprise matures). While the CNAS injunction
to pursue the “greatest feasible variety of weapons effects” is probably too ambitious, as well as unaffordable, the aggressiveness of the research and development (R&D) program for nuclear weapons is a key indicator of how seriously the United States is pursuing
this recommended strategy.


Preparing for twenty-first-century nuclear employment scenarios requires more than extending the life of a nuclear posture designed for the Cold War era. After thinking through how nuclear weapons might be employed against
the United States and its allies, the DoD must develop the concepts of operation (CONOPs) for countering them and then acquire the requisite capabilities. U.S. forces need to be trained (and exercised) in how to employ nuclear weapons in the manner prescribed
by the CONOPs. This is what it means to have an “effective deterrent as long as nuclear weapons exist.”


The design principles for the nuclear posture recommended here are grounded in common sense—form follows function, get the right capabilities for critical jobs, and capabilities (actions) speak louder than declaratory policy
(words). The two primary missions for U.S. nuclear weapons are deterrence and extended deterrence, and the future
force should be structured accordingly. In order to execute its Measured Response strategy, both forces should have low-yield, accurate, special-effects (Enhanced Radiation Weapon [ERW], Electromagnetic Pulse [EMP], “clean,” etc.) options that are employable
at the lower end of the nuclear continuum.


• Strategic Deterrent Force (SDF), consisting of Ohio-replacement class submarines, Minuteman III ICBMs (or a follow-on ground-based strategic deterrent [GBSD]), and B-52s and B-2s (and a new nuclear-capable bomber at some
point) is the highly survivable, assured destruction force that is the foundation on which U.S. nuclear deterrence resides. This is the “strategic triad” that deterred the Soviet Union during the Cold War and provides the United States its “nuclear shadow”.
• 战略威慑部队(SDF)，包括哥伦比亚级核潜艇（取代俄亥俄级），民兵3型弹道导弹（或计划中的新型弹道导弹：“陆基战略威慑”GBSD），B-52和B-2轰炸机（以及未来具有核能力的新型轰炸机）是一支具有高生存力和“保证摧毁”能力的部队，这是美国核威慑的基础。这一“战略核三角”在冷战期间成功威慑了苏联，并为美国提供了“核阴影”。

• Both the American people and policymaking elites have great confidence in the “second-to-none” status provided by its superior submarine-based nuclear forces. They are expensive, to be sure, but highly valued (and feared).
• 美国民众核决策者都对其世界第一的海基核力量拥有充分信心。它们（核潜艇）十分昂贵，但价值极高，并被敌人恐惧。

• ICBMs stabilize the “balance of terror” by raising the bar for a successful preemption attack to very high levels.
• 陆基洲际弹道导弹极大提升了先发核打击的成功门槛，从而稳定了“恐怖平衡”。

• ICBMs also hedge against the potential vulnerability of SLBMs (and their small number of aim points), because technological advances could render them visible.
• 陆基洲际弹道导弹避开了潜射弹道导弹的潜在脆弱性（以及有限的瞄准点数量），因为科技进步可能让潜艇“显形”。

• Discriminate employment options, delivered both by gravity bombs and a new cruise missile, would be provided by the same suite of air-delivered discriminate warheads used for extended deterrence.
• 有区分度的实战核武器，例如自由落体炸弹和新型巡航导弹，可以和延伸核威慑共用空基投送手段。

• While most of the low-yield warheads would be deployed on forward-based forces, the SDF should have a capability for discriminate employment to ensure that the full range of nuclear attacks against the U.S. homeland can be responded
to proportionately.
• 虽然大多数低当量核武器会被前置部署的部队持有，战略威慑部队仍应能投送低当量核武器，以确保对美国本土一切程度的核打击都将得到对等报复。

• Extended Deterrent Force (EDF), consisting of forward-based and rapidly deployable platforms would enable both permanent and temporary “coupling” of the U.S. nuclear deterrent to host-nation security.
• 延伸核威慑部队（EDF），包括前置部署和快速部署平台，既能暂时也能永久地将驻在国的安全和美国的核威慑“耦合”起来。

• Dual-capable F-35As (based on land) and F-35Cs (based on carriers) would provide visible manifestations of U.S. extended deterrence and allied burden-sharing.
• 多功能的F-35A（陆基）和F-35C（舰载）是对美国延伸核威慑和盟友“责任共享”的可见宣示。

• Discriminate employment options would be provided by a suite of low-yield, special-effects warheads (low collateral damage, enhanced radiation, earth penetration, electromagnetic pulse, and others as technology advances),
including possibly a smaller, shorter-range cruise missile that could be delivered by F-35s.
• 有区分度的核实战选项包括一系列低当量，有特殊效应（低连带损伤，增强辐射，钻地，电磁脉冲，其他效应），还可能包括一种F-35可携带的尺寸较小，射程较短的巡航导弹。

In this recommended 2025–2050 nuclear posture, bombers serve as an all-purpose hedge force that can enable, complement, and hedge for the other three “legs” (SLBMs,
ICBMs, and dual-capable F-35s). They provide extended deterrence presence and discriminate nuclear options in regions where there are no forward-based or deployed F-35s. They can also provide weapons and mobility to deploying F-35As. As the traditional complement to
SLBMs and ICBMs in the SDF, bombers are the most flexible leg of the strategic triad and can be used for signaling.


Currently, the United States has a nuclear force that consists of SLBMs, ICBMs, and two air-breathing variants (bombers and forward-based F-16s). This recommended 2025–2050 posture would have the same mix of systems, but with
a much enhanced capability for discriminate nuclear responses and forward deployment.


The capabilities envisioned for this recommended nuclear posture include weapons intended to deter nuclear attacks at the lower end of the nuclear continuum; forward-based and forward-deployable delivery systems intended for
extended deterrence; and assured destruction weapons that have intercontinental range, larger payloads, and are
deployed in numbers sufficient to ensure stability and survivability. These are the right capabilities for nuclear deterrence in the twenty-first century because they counter the
“nuclear offset” that U.S. adversaries might adopt for coping with U.S. conventional superiority.



Years 2025–2050 are too far into the future to project specific numbers. There are too many uncertainties—the state of U.S.-Russian arms control, the number of regional nuclear powers, and the mix of conflict, competition,
and cooperation between the major powers, to name a few. However, the following are offered as guidelines for sizing the 2025—2050 U.S. nuclear force:


• Maintain rough parity with Russia. Sustaining strategic stability, as well as regional stability in Europe, with a Russia that believed it had nuclear superiority would be significantly more difficult, if only because of
the likely impact on Russia’s propensity to take risks.
• 同俄罗斯维持大体均衡。如果俄罗斯确信它拥有核优势，保持战略稳定核欧洲地区稳定就会更加困难，这是因为这种优势会导致俄罗斯倾向于冒险。

• In order to build nuclear forces capable of responding proportionately to a nuclear attack at any rung of the escalatory ladder, the United States will have to address the significant disparity (with Russia) in nonstrategic
nuclear forces. In light of Russia’s rather crude nuclear diplomacy during the 2014 Ukraine crisis, the United States needs to address this capability gap as it strengthens the portion of its nuclear forces that are tailored for the extended deterrence mission
(to be discussed shortly).
• 为了在核升级的任一阶梯上都能进行对等反击，美国需要解决战术核武器显著落后于俄罗斯这一问题。根据2014年乌克兰危机期间俄罗斯相当粗糙的核外交政策，美国需要弥补其能力阶梯上的这一空当，并增强担负延伸核威慑的核力量（见下文）。

• Maintain nuclear superiority with China. Despite a numerical disparity that might be 10 to one, China’s assured-retaliation capability has gained it a strategic-stability relationship with the United States that, as DoD acknowledges
in the 2010 NPR report, is similar to that between the United States and Russia. However, China’s
overt achievement of nuclear parity with the United States (and Russia) would likely trigger regional proliferation by American allies, much as the Soviets did in Europe
during the Cold War. Avoiding this outcome could help explain China’s relative moderation in growing its nuclear forces.
• 维持对中国的核优势。尽管美国对中国的核武器数量优势可能是十比一，中国的已经有足够的核报复能力来维持同美国的战略稳定关系，正如国防部在2010年NPR(Nuclear Posture Review)报告中所称，这种关系类似于美俄之间的战略稳定。然而，若中国公开宣示同美俄相当的核力量，就可能导致区域内其他国家倒向美国，正如冷战期间苏联在欧洲导致的那样。这或许能够解释中国相当温和的核力量发展计划。

• Maintain sufficient capability to cope simultaneously with nuclear-armed “regional rogues.” States willing to contemplate employing a nuclear weapon in a conflict with the United States will also be willing to “bandwagon”
against the United States or “pile on” if the United States is distracted by another crisis.
• 保持同时应对拥核“地区流氓”的能力。设想在冲突中对美国使用核武器的国家或许会在美国被另一场危机吸引时“趁火打劫”。

• A world of 18 nuclear powers could include, in addition to the current nine members, Iran, Saudi Arabia, Egypt, Turkey, Japan, South Korea, Poland, South Africa, and Brazil.
• 除现在9个有核国之外，未来可能会多出伊朗、沙特阿拉伯、埃及、土耳其、日本、南韩、波兰、南非和巴西，一共18个有核国。

• Maintain a smaller stockpile, which is enabled by responsive infrastructure. The nuclear complex supporting a strategy of Measured Response is one that will design, develop, and produce new capabilities and new weapons. No
longer will Cold War-era weapons have to be retained as a technological hedge in the stockpile, which now has about 5,000 weapons in it.
• 削减（老旧的）核武库。“慎重反应”战略需要设计、研发和制造新型武器。冷战时代的武器将不再被作为“保底”手段，现在大约有5000枚此类武器。

Under New START limits and counting rules, the United States will have 1,550 operationally deployed nuclear weapons (with intercontinental range). With a responsive infrastructure, it could have a similar number of reserve
warheads. However, this does not address the disparity in U.S.-Russian nonstrategic nuclear weapons.


Final Thoughts 最后的话

Nuclear weapons have awesome destructive power—so awesome, in fact, that the leaders of nation-states have been inhibited in their willingness to risk their actual employment. While this has often been characterized as the
“nuclear taboo,” the unwillingness to risk nuclear escalation has been a rational calculation, not a values-based one. The contestants during the Cold War were afraid to break the nuclear threshold because they believed it would escalate quickly to general
nuclear war. This fear contributed greatly to keeping the Cold War cold.


U.S. conventional superiority, even if less dominant than it was at the time of the first Gulf War, is making the nuclear option more rationale for potential U.S. adversaries. For
those countries that do not want to live under Pax Americana and do not want to lose a conventional conflict with the United States, a plausible move is to employ a nuclear weapon and break the nuclear threshold in a manner that demonstrates their resolve but without
triggering the mass destruction of a nuclear war. The United States needs to undercut the desirability of the nuclear escalation to would-be opponents. By adopting the nuclear strategy and posture recommended here, the United States will have demonstrated
its willingness (if necessary) to engage at the nuclear level and, by doing so, will make it less likely that its opponents will do so. As was the case during the Cold War, preparing for nuclear war, if done seriously, made it less likely to happen. Hopefully,
that will prove to be the case in the “second nuclear age” as well.


