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We acknowledged progress in autonomy and Collaborative Combat Aircraft, including plans to enable increased Japan–Australia collaboration on MQ-28A under the Provision of Defence Articles and Defence Services Memorandum of Arrangement, and Japan Air Self Defence Forces (JASDF) participation in MQ-28A flight test observation and training in 2026.

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To grow quickly enough to be effective in a future conflict, the U.S. submarine fleet should incorporate diesel-electric air-independent propulsion boats.
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Concluding sections:

The Challenges of Reintroduction

Reintroducing diesel-electric submarines to the U.S. fleet presents challenges that extend beyond technical considerations. At the top of that list is the Navy itself. Diesel-electric boats are not part of the Navy’s vision. Introducing a new major platform would require a shift in the Navy’s undersea strategy, budgeting, manning, and training.

Within the Navy, the support of the submarine force would be paramount. The nuclear submarine force has evolved into an elite community with deeply ingrained beliefs about what constitutes excellence. Reintroducing diesel-electric submarines would require navigating complex questions about communities, status, career progression, and institutional identity.

Would service on diesel submarines carry the same prestige as nuclear assignments? Would diesel submarine commanders have equal promotion opportunities? How would the unified submarine force maintain its cohesion if split between nuclear-powered and conventional platforms?

The nuclear navy ethos—characterized by high technical standards, rigorous qualification processes, and elite status—represents a cultural achievement worth preserving. Any introduction of diesel submarines must address legitimate concerns about diluting this culture while creating space for complementary capabilities.

Reintroducing diesel-electric submarines would require substantial infrastructure development, even if the boats were built elsewhere. New maintenance facilities with expertise in diesel propulsion, battery systems, and AIP technologies would be needed. Supply chains for parts and components would need to be developed. Homeporting decisions would require facilities suitable for diesel submarine operations.

Training would be another challenge. The nuclear training pipeline—among the most rigorous in any military—produces submariners with deep expertise in nuclear propulsion. A diesel submarine force would require a parallel pipeline or adapting existing programs to accommodate different propulsion technologies without compromising standards.

Perhaps the greatest challenges lie in the political and industrial realms. The nuclear submarine industrial base is a national security asset developed over decades with substantial investment. Stakeholders would question whether introducing diesel submarines might divert resources, attention, or political support from nuclear programs. The perception of competition between nuclear and diesel programs could create zero-sum thinking that could undermine the complementary nature of the proposal.

In addition, the U.S. Navy and Congress would need to decide whether to develop indigenous diesel submarine construction capability or purchase platforms from allies. Both approaches present complex tradeoffs between speed of acquisition, technology transfer, industrial development, and alliance politics.

These are just some of the challenges that must be overcome to successfully reintroduce diesel-electric submarines to the fleet. While the questions and challenges appear substantial, they are not insurmountable. Preserving and extending U.S. undersea supremacy will require boldness, thoughtful planning, and institutional leadership.

Alternate Paths

The diesel-electric submarine route is not the only viable path toward this end. The Navy could increase the demand signal and funding for nuclear submarines. Such a plan would be more expensive both in ship and yard conversions but it is possible. The Navy could double down on LUUVs, hoping to overcome the challenges in those systems. Specifically, the service would need to solve either the persistent communication problem to enable reliable man-in-the-loop operations or solve the ethical problem of letting artificial intelligence act independently in strike missions.

The diesel-electric path seems more controllable, more reliable, and likely more effective. Modern diesel submarines are not perfect, but they are cost-effective, stealthy, and could be built quickly. It also is worth noting that this is not the first proposal for reintroducing diesel-electric submarines to the U.S. fleet. Independent strategists and think tanks have made similar pitches (See “Conventional Submarines Would Bring Affordable Lethality to the U.S. Fleet,” pp. 32–37.) Various approaches—research and development, contractor-owned/contractor-operated, or expanded partner-nation cooperation—also could allow the United States to investigate the benefits of diesel without committing immediately.

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Then there are the areas where these boats have the advantage—shallow, constrained waters in which their smaller size and displacement enable missions that would ground SSNs. Diesel-electric submarines can lurk quietly to conserve power and minimize detectability. Here, they can monitor traffic, gather intelligence, or lie in wait for targets while presenting minimal detection opportunities.

Such a capability would be invaluable in choke points such as the Taiwan Strait, Malacca Strait, Persian Gulf, Baltic Sea, Black Sea, or the Greenland, Iceland, and United Kingdom (GIUK) Gap, where water depths often fall below 60 meters. These are the tactics Russia employs with its diesel-electrics.

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There is a view, which I share, that SSKs are better suited to operations in the littoral environment particularly in constrained waters. Modern SSKs are very different from the previous generations of slow boats with limited non-diesel endurance. My interpretation of Jordan Spector's thesis is that they are a much cheaper way to supplement the SSNs in roles that don't need their expensive capabilities.

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