The 2023 Strategic Posture Commission Report From a Japanese Perspective

Masashi Murano, The 2023 Strategic Posture Commission Report From a Japanese Perspective, No. 610, January 6, 2025

Masashi Murano
Masashi Murano is a senior fellow with Hudson Institute’s Japan Chair.

U.S. allies are interested in America’s strategic posture because it has a direct bearing on the credibility of U.S. extended deterrence guarantees. The 2023 Strategic Posture Commission report comprehensively addresses the qualitative and quantitative efforts needed by the United States to address China and Russia, i.e., the two-nuclear-peer problem. Its recommendations support strengthening the credibility of U.S. extended deterrence in the Indo-Pacific region—a conclusion that would have been positively received had it been emphasized in the 2022 Nuclear Posture Review (NPR).

While generally supportive of many of the Commission’s recommendations, this paper provides a complementary argument for improving the credibility of U.S. extended deterrence in the Indo-Pacific region from a Japanese perspective and an alternative option that differs slightly from the Commission’s recommendations.

Balanced SSBN Forward Deployment Patrols

As pointed out in the Commission report, one of the biggest challenges to the U.S. regional deterrence posture is the lack of theater-focused nuclear capabilities in the Indo-Pacific. Strategic nuclear submarines (SSBNs) equipped with the Trident D5 submarine-launched ballistic missile (SLBM) can strike Chinese or North Korean targets within 30 minutes, even if patrolling near the U.S. West Coast. For this reason, some U.S. experts believe that the patrol area of the SSBNs is not that important in terms of their deterrence effect. However, a visible demonstration that SSBNs are deployed in the Western Pacific region with some frequency can be expected not only to aid in deterring China and North Korea from the temptation to attempt a limited nuclear attack, but also to assure allied publics.

While many analysts typically think of U.S. extended deterrence threats and the capabilities that support those threats in the context of deterring conflict before it begins, U.S. allies also expect U.S. extended deterrence threats to function in a conflict. Or, if deterrence cannot be controlled at a certain level, then U.S. damage limitation capabilities must be sufficient to meet allied needs. In short, U.S. allies with little strategic depth must, by necessity, consider the adequacy of prompt and effective U.S. damage limitation capabilities as part of their extended deterrence requirements.

For example, in a situation where the adversary is about to escalate after considerable conventional exchanges have taken place and Japan’s missile defense capacity has been severely eroded, or, in a worst-case scenario, a nuclear first strike against Japan, the United States and Japan must focus on limiting further damage using all available capabilities. In such a case, the capability to carry out rapid counterforce strikes against time-sensitive targets such as dispersed mobile nuclear missiles is required. In such an extreme situation, launching the Trident D5 from a forward-deployed SSBN in the waters surrounding Guam would be able to neutralize potential Chinese and North Korean targets in approximately 13-15 minutes.[1] At present, there is no other system that can guarantee better readiness, survivability, penetration capability against air defense systems, and wide-area suppression capability than the Trident D5 with the W76-2 warhead.

It is undeniable that the future development of advanced unmanned systems and quantum technology will dramatically improve the anti-submarine warfare (ASW) capabilities of U.S. and Japanese adversaries. However, at this moment, given the series of kill chains for identifying, tracking, and evaluating attacks on U.S. SSBNs, it is likely that submarines will maintain their superiority for the foreseeable future over all other platforms, including land-based mobile missiles, aircraft, and surface vessels, in terms of survivability from all types of nuclear and non-nuclear attacks. Therefore, the highest priority should be placed on submarine-based systems when considering the credibility of U.S. extended deterrence in the Indo-Pacific region.

On the other hand, in light of China and North Korea increasing their theater strike capabilities, having valuable SSBN calls at Northeast Asian allies’ ports has many military disadvantages that may outweigh the benefits in terms of deterrence and reassurance. The timing of the SSBN’s port call is a great opportunity for China and North Korea to strike, and in a crisis, it may in fact encourage the adversary to launch a preemptive strike. Also, forward port calls could provide an opportunity for China and North Korea not only to gather information, but also potentially present an opportunity for detection from Russian submarines and patrol aircraft. Thus, while SSBN port calls to Japan and South Korea may be feasible in peacetime, they are unlikely during a crisis or conflict. Considering the balance between deterrence effect and vulnerability, it would be most appropriate to limit SSBN operations to port calls and patrols in the area surrounding Guam.

In past U.S. NPRs and the Commission report, Dual-Capable Aircraft (DCA) have been described as having a complementary role to the strategic nuclear triad. However, the theater strike capabilities of China and North Korea call into question the global deployability of the DCA, and even strategic bombers. Stealth aircraft such as the B-2 bomber and F-35 DCA, like submerged SSBNs, are difficult to detect and intercept once they take off, so if China and North Korea are to neutralize them, their best bet is to destroy them immediately with ballistic missiles when they are on the ground. Therefore, forward deployment of bombers and DCA on U.S. bases in Japan and Guam might incentivize preemptive strikes by adversaries in a situation of heightened crisis. It also takes more than an hour for an F-35 sortie from Japan to penetrate the skies over China or North Korea and drop a B61-12 nuclear bomb, or for a subsonic nuclear cruise missile such as the U.S. AGM-86B or Long-Range Stand-Off (LRSO) missile launched from a B-52 or B-21 flying around Japan to impact its target, both of which are potentially not effective counterforce strike options for targeting mobile nuclear missiles that are about to start their launch sequence.

These facts mean that there is a difference in the impact of DCA on the adversary’s deterrence calculus between Europe, where DCA are already deployed on a regular basis, and the Indo-Pacific, where their potential deployment in a crisis is problematic. In other words, as well as SSBN port calls to Korea, the forward deployment of strategic bombers or DCA may represent a political symbol for assurance that can be carried out only in peacetime, but it has little military effectiveness in a crisis that requires the demonstration of effective deterrence. Thus, forward deployment of DCA (and NATO-like nuclear sharing agreements regarding DCA) are hardly adequate options for strengthening U.S.-Japan extended deterrence. An option that could both deter and provide assurance signaling, while also helping to mitigate this vulnerability, would be to increase the frequency of aerial patrols around Japan, rather than landing strategic bombers at U.S. bases in Japan or Korea. As will be described below, Japan’s expanding tanker fleet should be able to meaningfully extend the patrol time of U.S. bombers.[2]

It is well known that the proposed sea-launched nuclear cruise missile (SLCM-N) remains one of the most controversial programs. As noted in the 2022 Nuclear Posture Review, the Trident D5 with the W76-2 provides an important contribution to flexible nuclear deterrence as a de facto theater nuclear capability.[3] However, the number of W76-2s deployed is extremely small. Their deployments should be increased as an option in line with the Strategic Posture Commission’s suggestions. But even so, another problem remains. For example, some in the Biden Administration have opposed the employment of the W76-2 on the grounds that because it is delivered by a strategic ballistic missile, it could be misunderstood by the adversary as a strategic nuclear strike.[4] If there are voices within the current administration that still take such risks seriously, then a survivable, non-ballistic, low-yield nuclear option should be necessary to help deter limited nuclear use.

However, as noted earlier, bombers and DCA, while relatively flexible and able to demonstrate visible deterrence threats, are slower than ballistic missiles and cannot remain in the same area for long periods of time. In addition, any attempt to land these aircraft at a South Korean or Japanese air base in a situation of heightened tension would make them easy targets for the medium- and intermediate-range ballistic missiles (MRBMs/IRBMs) that China and North Korea are building. These risks also arose when the United States deployed ground-based nuclear missiles such as Pershing II.

Therefore, the new theater-focused nuclear option must:  (1) have greater flexibility than SSBNs, which are limited in number; (2) be able to remain in the same area longer than aircraft; (3) be more survivable while deployed; (4) have high penetrability against advanced air defense systems; and, (5) be capable of carrying low-yield nuclear warheads.

The first theater-based nuclear option that would satisfy these requirements would be the development and deployment of the SLCM-N. However, the Commission report does not clarify how long it would take to deploy the SLCM-N. According to the FY2024 National Defense Authorization Act, the target date for achieving initial operational capability of the SLCM-N is 2034 at the latest.[5] What was lost by the initial cancellation of the SLCM-N program is not only a flexible theater-focused nuclear capability, but also valuable time.

If development and deployment of SLCM-N as a feasible, sea-based, theater-focused nuclear capability does not happen quickly, then the United States should consider developing an intermediate-range nuclear prompt strike (IR-NPS) system—a variant of the planned U.S. Navy conventionally-armed intermediate-range prompt strike weapon. The intermediate-range conventional prompt strike (IR-CPS) is scheduled to be integrated with Virginia-class nuclear-powered fast attack submarines (SSNs) in 2028 to achieve full operational capability. As a first effort, the U.S. Navy and the national laboratories should conduct a technology demonstration to modify and load existing or newly developed nuclear warheads on the 34.5-inch, two-stage rocket motors designed for the IR-CPS.[6] Initial deployment of the U.S. Army’s long-range hypersonic weapon (LRHW), which shares most of the IR-NPS’s design, is coming in 2024.[7]

If the priority is to accelerate deployment, there is no need to put a nuclear warhead on the common-hypersonic glide body (C-HGB), which is designed as a conventional hypersonic glide vehicle. A combination of a traditionally designed nuclear warhead and rocket motors can be operated as a submarine-launched medium/intermediate-range ballistic missile. Once hypersonic glide technology has matured, a phased upgrade to integrate nuclear warheads with the C-HGB would maintain a maneuverable theater nuclear option that could penetrate Russian and Chinese missile defenses, even if their systems become comparable to those of the United States and Japan in the future. With New START largely invalidated by Russia’s suspension of implementation, there are no arms control agreements to prohibit deployment of the IR-NPS, and by the time the IR-NPS is ready for deployment, New START will have expired anyway.

The Commission’s recommendations focus mainly on the U.S. strategic posture, with limited descriptions of non-nuclear (conventional) capabilities. However, U.S. conventional capabilities and those of its allies have important roles in supporting the credibility of U.S. extended deterrence.

For example, the reported range of LRHW will not reach mainland China even if it is deployed to Guam. In other words, LRHW will be of little deterrent utility in the Indo-Pacific unless it is forward deployed to allied countries such as Japan and the Philippines. The sooner the LRHW is deployed to Japan, the better, to close the strike capability gap with China as soon as possible. For this reason, the United States should work with Japan to begin training for the rapid deployment of LRHWs. The United States and Japan could work together to construct additional munitions depots and support facilities for dispersed deployment at several Japan Ground Self-Defense Force maneuver areas located in Kyushu, Honshu, and Hokkaido. U.S. LRHWs or Japanese counter-strike capabilities can place fixed targets such as command, control, and communications (C3) nodes associated with adversary mobile missiles at risk. Given that almost all missiles China and North Korea possess are dual-capable, there is a natural risk of nuclear escalation when targeting their associated systems. In other words, close and seamless escalation management between Japan and the United States is essential, even if it is a strike operation using conventional weapons. Through the counter-strike capabilities that Japan is building and integrating with U.S. non-nuclear capabilities, Japan has a responsibility to jointly manage escalation control efforts with the United States. Consequently, Japan should ask to become involved in U.S. nuclear operational planning. This is more in line with the current needs of the times and U.S. and Japanese capability requirements than with a NATO-like nuclear sharing arrangement based on the DCA and the B61.

For the U.S. extended deterrence commitment to be credible, it is important that the United States remains relatively safe from an adversary’s coercive attacks. However, as the Commission report emphasizes, the currently planned U.S. homeland defense posture, by design, does not have sufficient capacity to deal with the limited possible threats that China, Russia, or North Korea could launch in the near future. One example is that North Korea continues to produce ICBMs and their mobile launchers in volume and Kim Jong-un has stated a willingness to move forward with the development of multiple independently-targetable re-entry vehicles (MIRVs). In addition, the de facto fractional orbital bombardment systems (FOBS), which combines ICBMs and hypersonic glide vehicles (HGVs) that China and Russia are developing and deploying, would provide the option of launching a limited strike on the United States without a massive ICBM salvo, while also evading existing homeland missile defense systems.

Japan should request and support U.S. efforts to further strengthen its homeland defense capabilities and capacities. In this regard, Japan should also consider applying the results obtained from the ongoing areas of early warning and tracking through satellite constellations and joint development of the Glide Phase Interceptor to enhance the U.S. homeland defense capability.

The Commission’s recommendations focus on the hardware supporting the U.S. nuclear posture, i.e., military capabilities, and thus have only limited reference to elements of software with allies, i.e., consultation mechanisms and planning processes. However, U.S. deterrence can only be credible with the appropriate mix of hardware and software, that is, military capabilities and cooperative efforts between U.S. and Japanese officials.

High-level and Multi-layered U.S.-Japan Extended Deterrence Dialogue

In contrast to the decision to use nuclear weapons in NATO, which is made through consultations not only with the United States but also with the political leaders of other NATO members, especially the United Kingdom and potentially France, the U.S.-Japan institutional framework for extended deterrence leaves the final decision-making authority on the use of nuclear weapons exclusively to the President of the United States.

However, the use of nuclear weapons, even in retaliation for an adversary’s nuclear attack, remains an extremely serious political decision, and in practice, the United States will likely seek the views of the parties to the conflict and allies outside the parties to the conflict. Asking the United States to strengthen the credibility of extended deterrence also means that Japan’s political leaders must be prepared to share with the U.S. President the historical and moral responsibility that comes with the use of nuclear weapons. In July 2024, U.S. and Japanese officials conducted the first round of U.S.-Japan Extended Deterrence Dialogue at the ministerial level, a significant step. However, a mere 20-minute ministerial meeting is not enough to cultivate the decisiveness necessary for political leaders.[8] For this reason, I recommend that the prime minister and key cabinet members regularly conduct table-top exercises with U.S. officials that involve the difficult decision to use nuclear weapons.

The NATO Nuclear Planning Group (NPG) has a multi-layered consultative framework according to the level of participation and the scope of discussions. This includes a ministerial group of defense ministers from member countries, a staff group to discuss and support the substantive agenda of the ministerial group, and a high-level advisory group consisting of representatives of directorates and experts from each country. Using these as examples, the U.S.-Japan extended deterrence talks should be updated in a manner that will result in a higher level and multi-layered commitment. Specifically, while retaining the biannual consultations at the Deputy Assistant Secretary of Defense level (i.e., the U.S.-Japan Extended Deterrence Staff Level Group), a ministerial-level (“2 plus 2”) group could be regularized, featuring table-top exercises simulating the use of nuclear weapons and could be held once a year with the participation of the U.S. Secretaries of State and Defense and the Japanese Foreign Affairs and Defense Ministers. This would give all government organizations, including the Self-Defense Forces (SDF), a mandate to support U.S. nuclear operations. In addition, a Track 1.5 advisory body (Extended Deterrence Committee), consisting of a staff-level group plus experts from Japan and the United States, should be established to support the identification of medium- and long-term issues related to extended deterrence, the development of various crisis scenarios, and appropriate outreach opportunities (strategic communication).

In the crises that Japan and the United States may face in the future, they will be required to deal with the difficult task of how to deter conventional war under the nuclear shadow and, if deterrence fails, how to fight and manage escalation in a proactive manner while bringing the war to a desirable termination. Therefore, U.S.-Japan joint operational planning for a Taiwan contingency and a Korean Peninsula contingency must be established in a manner that seamlessly links joint conventional operations, including the use of counterstrike capabilities, from responses in the gray zone to up to the conduct of U.S. nuclear operations with Japanese support. To make this possible, discussions in the Extended Deterrence Consultative Staff Level Group must be institutionally integrated with the work on joint planning under the U.S.-Japan defense guidelines.

In formulating a U.S.-Japan joint operational plan, the two countries must constantly review and share actual operational challenges through repeated field and tabletop exercises involving U.S. forces in Japan and South Korea, INDOPACOM, STRATCOM, and other functional commands. In this regard, what is currently lacking in Japan and the United States is a discussion on what roles and missions the SDF will assume when the U.S. military conducts nuclear operations. It has long been a regular practice between Japan and the United States for U.S. strategic bombers and Self-Defense Force fighter jets to conduct joint flight training exercises after North Korean missile tests and other such events. However, these joint drills are mostly for show and are not tied to actual nuclear operational planning as they do not involve coordination of procedures and targeting of nuclear strikes by U.S. strategic bombers. In contrast, NATO conducts an aerial tactical drill called SNOWCAT (Support of Nuclear Operations with Conventional Air Tactics) as part of Steadfast Noon, a joint exercise that assumes that nuclear weapons will be employed. SNOWCAT is intended to support nuclear operations of nuclear sharing partners by ensuring the security of the surrounding airspace by fighter jets such as those of Poland and the Czech Republic, which are non-nuclear sharing partners. As a result, the non-nuclear sharing partners can share some of the information and planning necessary for cooperative operations. Japan and the United States should also use the timing of forward deployed U.S. strategic bombers and SSBNs as an opportunity to shape discussions on the possible coordination of SDF conventional capabilities and U.S. nuclear capabilities. For example, Japan and the United States could begin training immediately for aerial refueling support by the Japan Air Self-Defense Force’s aerial tankers for U.S. strategic bombers. Such activities would reduce the vulnerability of bombers by extending their patrol time, demonstrating collective resolve to adversaries, and promoting information sharing on nuclear operations by the United States with its allies.

In the past, the United States had a global nuclear war plan called the Single Integrated Operational Plan (SIOP). Later, as the possibility of all-out nuclear war diminished with the end of the Cold War, the SIOP was abandoned in 2003, and the U.S. nuclear employment plan was replaced by regionally-tailored approaches and individual operational plans (OPLANs). However, as the Commission has repeatedly emphasized, the risk of having to deal simultaneously with two near-peer nuclear-armed adversaries in the face of increasingly constrained resources is becoming apparent. Given this, it is not necessarily sufficient to simply plan and design separate OPLANs designed, for example, only for Taiwan, the Korean Peninsula, Europe, or the Middle East.

If Russia were to expand the scope of its offensive to NATO member states or to embark on a limited use of nuclear weapons, and the United States chose to respond with conventional forces to avoid escalation to the nuclear-level, the response can be expected to consume many long-range precision-guided munitions, such as sea- and air-launched cruise missiles. If a Taiwan contingency or a Korean Peninsula contingency were to occur several years later, without restocking, stockpiles of long-range precision-guided munitions and interceptor missiles could be depleted, and the United States could be forced to resort to nuclear weapons in the early stages of a conflict. To deal with such complex problems, if crises and wars occur simultaneously or in succession in multiple theaters, the United States should conduct a single integrated global exercise with allies including Japan, South Korea, Australia, Taiwan, and NATO, to verify the status of competition for weapons and munitions needed in each region, and the strength of the supply chain. Then, to efficiently identify any shortfalls, it is necessary to establish a federated logistics management mechanism through the rapid development and adoption of interface software that links the different supply and logistics management tools used in Japan and the United States. As a first step in this effort, it is important to integrate the supply and logistics management of the same services that use partially common equipment – the U.S. Navy and the JMSDF, and the U.S. Air Force and JASDF.

In addition to U.S.-Japan consultations, the United States should diversify its extended deterrence consultations to bring together stakeholders from various regions such as Japan-U.S.-ROK, Japan-U.S.-Australia, Japan-NATO, and Japan-U.S.-Taiwan to promote, share, and deepen the development, planning, and coordination of joint operations. Specific examples include the establishment of Track 1.5 consultations where South Korean experts are mutually invited to the U.S.-Japan Extended Deterrence Dialogue and Japanese experts to the U.S.-ROK Nuclear Consultative Group, and regular exchanges between NATO’s High Level Group and Japanese and South Korean participants in the extended deterrence dialogue.

In addition to regular joint U.S.-Japan exercises, U.S. allies have accumulated deep knowledge and expertise through the dispatch of liaison officers to U.S. combatant commands and various military command and staff colleges. On the other hand, systematic efforts to understand the nuclear operations and planning process have been very limited. Even though the United States is not required to disclose individual nuclear operational plans to its allies, it could better facilitate their understanding of the general process for planning and executing nuclear operations. Therefore, STRATCOM should provide regular educational opportunities for staff-level foreign and defense officials including military officers in Japan and South Korea. Such an effort would also provide a unique opportunity to share thoughts on how staff supporting political leaders at the presidential/prime ministerial and ministerial/secretarial levels should communicate with them in extreme circumstances when decisions must be made regarding the potential use of nuclear weapons.

The United States and its Northeast Asian allies have gradually updated their hardware and software over the past 15 years to maintain the credibility of extended deterrence. Nonetheless, as the Strategic Posture Commission points out, U.S.-Japanese adversaries are attempting to undermine the credibility of U.S. extended deterrence at a more rapid pace. While there is not much to be optimistic about in the current security environment, there is at least one positive development: many of the issues have already been identified with bipartisan consensus by the Commission and the experts it consulted. The United States and its allies should take concrete actions to resolve them as soon as possible, and hopefully the recommendations made in this article can aid in that process.

This article appeared originally at National Institute for Public Policy.

[1] On unclassified estimates of flight times, see, Congressional Budget Office, U.S. Hypersonic Weapons and Alternatives (Washington, D.C.: CBO, January 2023), p. 35, available at https://www.cbo.gov/publication/58924.

[2] The Japan Air Self-Defense Force is gradually acquiring KC-46As in addition to the four KC-767s it originally had, and the current plan is to expand its tanker fleet to 19 tankers. U.S. Defense Security Cooperation Agency, “Japan – KC-46A Aerial Refueling Aircraft,” DSCA.mil, September 13, 2024, available at https://www.dsca.mil/press-media/major-arms-sales/japan-kc-46a-aerial-refueling-aircraft.

[3] U.S. Department of Defense, 2022 Nuclear Posture Review (Washington, D.C.: Department of Defense, 2022), pp. 11, 20, available at https://media.defense.gov/2022/Oct/27/2003103845/-1/-1/1/2022-NATIONAL-DEFENSE-STRATEGY-NPR-MDR.pdf.

[4] For example, see, Vipin Narang, “The Discrimination Problem: Putting Low-Yield Nuclear Weapons on Submarines is So Dangerous,” War on the Rocks, February 8, 2018, available at https://warontherocks.com/2018/02/discrimination-problem-putting-low-yield-nuclear-weapons-submarines-dangerous/. In the first place, the risk of a single shot by D5LE2 being misunderstood as a strategic nuclear attack is not necessarily high, since a full-scale first strike for the purpose of disarming, and a single SLBM launch for the purpose of responding a limited nuclear use have different signatures that can be detected by early warning capabilities.

[5] H.R.2670 – National Defense Authorization Act for Fiscal Year 2024. Robert Soofer, “The US is building a nuclear sea-launched cruise missile. Congress must make sure it’s built right.”Atlantic Council, April 3, 2024, available at https://www.atlanticcouncil.org/blogs/new-atlanticist/the-us-is-building-a-nuclear-sea-launched-cruise-missile-congress-must-make-sure-its-built-right/.

[6] On the motors, see, U.S. Navy, “Navy Hypersonic Rocket Motor Moves Closer to Flight Testing,” Navy.mil, October 29, 2021, available at https://www.navy.mil/Press-Office/News-Stories/Article/2827117/navy-hypersonic-rocket-motor-moves-closer-to-flight-testing/.

[7] Jon Harper, “Army hopes to field Dark Eagle hypersonic missile in summer 2024 after resolving problems with launcher,” Defense Scoop, December 03, 2023, available at https://defensescoop.com/2023/12/03/army-hopes-to-field-dark-eagle-hypersonic-missile-in-summer-2024-after-resolving-problems-with-launcher/.

[8] U.S. Department of Defense, “Joint Statement of the U.S.-Japan Ministerial Meeting on Extended Deterrence,” Defense.gov, July 28, 2024, available at https://www.defense.gov/News/Releases/Release/Article/3852173/joint-statement-of-the-us-japan-ministerial-meeting-on-extended-deterrence/.

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