The Strategic Transformation of the People's Liberation Army Navy: The Deep Logic Behind the Shift from Diesel-Electric to Fully Nuclear Submarine Construction

The U.S. Navy's intelligence chief, Rear Admiral Mike Brookes, disclosed in written testimony submitted to the U.S.-China Economic and Security Review Commission this week that the People's Liberation Army Navy (PLAN) is executing a "major strategic transformation from diesel-electric submarines to a fully nuclear submarine fleet." This statement reflects a fundamental shift in the Chinese Navy's underwater combat capability development, with strategic implications that far exceed mere equipment upgrades.

According to Brookes' assessment, the Chinese Navy currently possesses over 60 submarines, of which at least 14 are nuclear-powered, including attack submarines, ballistic missile submarines, and cruise missile submarines. Although diesel-electric submarines still constitute the majority of the fleet, through significant investments in three major shipyards, major construction projects, and infrastructure upgrades, China has increased its annual production of nuclear submarines from "less than one" to "a significantly higher rate." These investments date back more than a decade, laying the industrial foundation for continued expansion into the 2030s and beyond.

This increase in production capacity will reshape the structure of the PLA Navy's underwater forces over the next decade. According to U.S. predictions, by 2027, the size of China's submarine fleet is expected to reach approximately 70 vessels, even considering the retirement of some older submarines built by China and Russia. More strategically significant is the long-term vision for 2035: by then, the total number of submarines is expected to increase to around 80, with about half being nuclear-powered. This means that within the next nine years, the proportion of nuclear submarines will leap from currently less than a quarter to nearly half, representing a qualitative leap.

Among the most notable developments in this transformation is the emergence of the Type 041 (Zhou-class) nuclear-powered attack submarine. This is an unusual design concept—a small nuclear submarine close in size to a diesel-electric submarine. Unlike traditional large nuclear submarines that focus on long-range oceanic missions, the Zhou-class submarines maintain the advantages of nuclear power while reducing costs and complexity. Although the first vessel sank at the Wuchang Shipyard between May and June 2024, the U.S. Department of Defense's report on Chinese military capabilities suggests that this may be related to capability deficiencies caused by corruption in defense procurement, this setback has not altered China's determination to advance a diversified nuclear submarine fleet.

Even more deterrent are the Type 095 cruise missile nuclear submarines and Type 096 ballistic missile nuclear submarines, which are set to enter service later this century and in the 2030s. Brookes emphasized that these new submarines will achieve "substantial advancements" in nuclear reactor design, sensor performance, weapon integration, and noise reduction technology. Particularly noteworthy is the Type 096 submarine, which will be equipped with JL-4 submarine-launched ballistic missiles, enabling it to strike "large areas of the United States" from "protected waters"—namely, China's coastal waters. This marks an important milestone in China's sea-based nuclear deterrent capability, as Chinese nuclear submarines will be able to cover most targets on the U.S. mainland without needing to break through the first island chain.

In parallel with the modernization of the submarine fleet, there is a systematic construction of an underwater surveillance network. Brookes' testimony revealed that China has deployed a multi-layered detection system in key waters such as the South China Sea, including satellite-linked buoys, unmanned underwater vehicles (UUVs), and underwater sonar arrays, to continuously monitor potential foreign submarine activities. These systems not only protect China's expanding nuclear submarine fleet but also pose challenges to U.S. and allied underwater operations both within and beyond the first island chain. China's decades-long investment in unmanned underwater vehicles is beginning to bear fruit, with these platforms designed as modular payload systems capable of executing strike or surveillance missions.

It is noteworthy that even as China transitions to a fully nuclear fleet, it has not completely abandoned diesel-electric submarines. Brookes mentioned that China is modernizing its diesel-electric submarines, such as the Yuan-class, using new technologies to enhance their endurance. This indicates that diesel-electric submarines will still play a role in the Chinese Navy's operational system, albeit with a gradually decreasing proportion. This "dual-track approach" maintains flexibility in coastal defense while strengthening long-range projection capabilities.

This strategic transformation of the submarine fleet is closely tied to China's broader maritime strategy. U.S. officials and Chinese observers have previously pointed out that China has lagged in nuclear propulsion technology, primarily constrained by training, technical issues, and equipment quality. However, the Pentagon's report acknowledges that China's ongoing development in propulsion technology has shown improvements in recent years. These investments are core pillars of China's efforts to build a blue-water navy, extending naval influence from the first island chain to the broader Indo-Pacific region and even to the Arctic and Atlantic.

From a macro perspective, this reconstruction of underwater power comes at a time when the Chinese military is facing internal turmoil. Xi Jinping's ongoing anti-corruption purge within the military has affected high-ranking members of the Central Military Commission, including the ousting of key figures like Zhang Youxia. While U.S. military assessments suggest that the impact of the purge on combat readiness is "temporary," the rapid modernization of the Chinese military will continue, but short-term disruptions in the command structure are inevitable. In this context, the technology-intensive construction of nuclear submarines may become a relatively "politically safe" area of modernization—relying on industrial foundations and technological breakthroughs rather than the personal capabilities of high-ranking generals.

At the same time, the PLA is required to achieve the capability for a "strategic decisive victory" over Taiwan by 2027 and to achieve "strategic balance" against the U.S. through nuclear capabilities and other strategic means. The expansion of the nuclear submarine fleet, particularly the deployment of the Type 096, will directly serve this timeline. A sea-based nuclear force capable of deterring the U.S. from its nearshore will become an important bargaining chip for China in countering U.S. intervention in a Taiwan Strait conflict.

The acceleration of China's nuclear submarine construction is also causing ripple effects globally. The U.S. Navy is facing delays in submarine construction and an aging fleet, while China's shipbuilding capacity—annual military ship and submarine construction numbers have surpassed those of the U.S.—provides it with a unique advantage. U.S. officials are calling for urgent action: to enhance submarine readiness and industrial supply chains; to deploy resilient underwater detection and counter-detection systems; to massively deploy unmanned underwater vehicles; to increase reserves of key underwater weapons and payloads; and to deepen intelligence sharing and training cooperation with allies. As U.S.-China competition intensifies, the U.S. must maintain its ability to operate freely underwater in the Indo-Pacific region.

The strategic transition from diesel to fully nuclear essentially represents another leap for China from coastal defense to open-ocean presence. This is not only a technological advancement but also an evolution in strategic thinking—from passive defense to proactive deterrence, from regional power to global player. In the next decade, this increasingly powerful and advanced nuclear submarine fleet will become an undeniable variable in the maritime security landscape of the Indo-Pacific and beyond.