China’s growing fleet of diesel-electric submarines, already among the most cost-effective undersea platforms in production, is becoming a sharper threat as Beijing works to integrate advanced strike capabilities, including hypersonic weapons, into its naval arsenal. The People’s Liberation Army Navy has been expanding its submarine force while simultaneously exporting affordable boats to allied nations, creating a dual challenge for the United States and its Indo-Pacific partners. With the Pentagon projecting significant growth in China’s undersea fleet over the next decade, the convergence of cheap submarines and fast-evolving missile technology is reshaping the military balance in contested waters near Taiwan and beyond.
Beijing’s Submarine Fleet on Track for Major Expansion
The scale of China’s submarine buildup is laid out in a Congressional Research Service report on Chinese naval modernization, which notes that the Department of Defense projects China’s submarine force could grow to roughly 80 boats by 2035. That fleet includes a mix of nuclear-powered ballistic missile submarines (SSBNs), nuclear-powered attack submarines (SSNs), and conventional diesel-electric attack boats (SS). The Yuan-class, designated Type 039A/B, forms a significant part of the conventional force. These diesel-electric submarines use air-independent propulsion, or AIP, which allows them to operate submerged for extended periods without surfacing to recharge batteries, making them far quieter and harder to detect than older diesel boats.
What makes this expansion strategically significant is not just the number of hulls but the cost calculus behind them. Diesel-electric submarines like the Yuan-class are dramatically cheaper to build and maintain than nuclear-powered alternatives. For a navy focused on regional denial rather than global blue-water operations, these boats offer an efficient way to threaten surface ships, enforce blockades, and complicate an adversary’s ability to operate freely in the western Pacific. The AIP technology in the Type 039A/B closes much of the stealth gap with nuclear submarines during short-duration patrols, giving China a capable platform at a fraction of the price. That combination of affordability and stealth underpins Beijing’s ability to scale up its undersea presence faster than rivals that rely primarily on more expensive nuclear-powered fleets.
Export Pipeline Extends China’s Undersea Reach
China is not just building submarines for itself. A Chinese shipyard recently completed a second diesel-electric submarine for Pakistan, part of a contract for eight Hangor-class boats. Some of those submarines are to be built in Pakistan, a co-production arrangement that transfers industrial know-how and deepens the defense relationship between Beijing and Islamabad. The Hangor-class boats are based on Chinese conventional submarine designs and represent a significant upgrade over Pakistan’s aging fleet, giving its navy longer reach and more modern sensors and weapons than older platforms.
This export model carries implications that go beyond a bilateral arms deal. By supplying affordable, capable submarines to partners, China effectively extends its strategic influence into new theaters without deploying its own forces. Pakistan, which has long viewed its submarine arm as a counter to India’s larger navy, gains a platform that could be armed with increasingly advanced weapons over time. The arrangement also keeps Chinese shipyards busy and production lines warm, supporting the industrial base that feeds the PLAN’s own expansion. In a crisis, even if there is no formal alliance, Chinese-designed submarines in foreign hands can complicate the operational picture for the United States and its partners, tying down surveillance and anti-submarine warfare assets that might otherwise focus on tracking the PLAN itself.
Hypersonic Missiles Multiply the Submarine Threat
The headline risk is not the submarines alone but what they might carry. According to the Pentagon, China has expanded its nuclear force and continued developing long-range strike capabilities, including hypersonic weapons, as part of a broader military modernization drive. The Defense Department’s annual China assessment, which is congressionally mandated, tracks these developments as part of PLA efforts to field weapons that can defeat missile defenses. Hypersonic glide vehicles travel at speeds exceeding Mach 5 and follow unpredictable flight paths, making them extremely difficult for existing air and missile defense systems to intercept and compressing decision times for commanders under attack.
Pairing such weapons with low-cost diesel-electric submarines would represent a qualitative shift. A quiet AIP submarine lurking in shallow littoral waters near Taiwan or in the South China Sea, armed with a hypersonic anti-ship missile, could threaten U.S. carrier strike groups or allied surface combatants at ranges and speeds that current defenses struggle to counter. No public evidence confirms that China has already deployed hypersonic missiles aboard its conventional submarine fleet, and the reporting gaps here are real: neither the Pentagon’s published assessments nor the CRS analysis provide specific integration timelines or test records for such a pairing. But the trajectory of both programs, submarine production and hypersonic weapon development, points toward eventual convergence. For the U.S. Navy and regional partners, planning against that possibility means investing in more capable sensors, faster decision-making tools, and new operational concepts that assume shorter warning times and more complex attack profiles.
Pentagon and Congressional Warnings Align
Two separate arms of the U.S. government have flagged these trends. The Pentagon’s China report, according to recent coverage, includes warhead estimates, Taiwan pressure indicators, and assessments of China’s strengthened military ties to Russia. Separately, the U.S.-China Economic and Security Review Commission published its latest annual study, a legislative-branch assessment that covers PRC security and defense developments, including maritime and Taiwan-related risks. The fact that both executive and legislative branch bodies are sounding alarms about the same set of capabilities reflects a rare degree of institutional consensus that China’s military modernization is eroding long-standing U.S. advantages in the Western Pacific.
The commission’s report provides strategic framing that complements the Pentagon’s more technical assessments. Where the Defense Department catalogs submarine counts, missile inventories, and specific programs, the congressional commission situates those capabilities within the political and economic dynamics of U.S.-China competition. Together, the two reports paint a picture of a Chinese military that is not only growing larger but becoming more capable of projecting power in ways that directly challenge American interests, especially around Taiwan and key sea lanes. For lawmakers, that convergence of analysis bolsters arguments for sustained investment in undersea warfare, missile defense, and regional alliances, while also underscoring that technology transfers and arms sales from China to partners like Pakistan can have ripple effects far beyond their immediate neighborhoods.
Implications for Deterrence and Regional Security
The intersection of China’s expanding submarine fleet, its hypersonic weapons program, and its growing defense export network is reshaping deterrence calculations across the Indo-Pacific. For the United States and its allies, the prospect of more numerous, quieter diesel-electric submarines operating alongside nuclear-powered boats forces a reassessment of how to protect high-value assets, from carriers to logistics ships, in contested waters. Traditional advantages in undersea warfare are under pressure as China leverages cost-effective platforms and incremental technology upgrades to close capability gaps. At the same time, the spread of Chinese-designed submarines to partners like Pakistan adds a layer of complexity to any regional crisis planning, since U.S. forces might face similar undersea threats in multiple theaters simultaneously.
Managing these risks will require more than platform-for-platform competition. U.S. and allied planners are likely to focus on improving anti-submarine warfare networks, integrating undersea surveillance with space-based and airborne sensors, and refining operational concepts that reduce the vulnerability of surface forces to surprise attack. Diplomatic efforts to build tighter security cooperation among Indo-Pacific partners can complement these military steps by improving information-sharing and joint training focused on undersea threats. Even if China never fully integrates hypersonic missiles onto its diesel-electric submarines, the possibility alone, combined with the documented growth in its undersea fleet and the spread of its designs abroad, has already altered the strategic landscape, compelling adversaries and neighbors alike to prepare for a more contested, less predictable maritime environment.
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*This article was researched with the help of AI, with human editors creating the final content.
