Last month, a Chinese-owned vessel was accused of cutting an undersea fiber-optic cable near Keelung Harbor, highlighting the vulnerability of critical communications infrastructure. While the incident caused only minor disruptions to Internet service, it aligned with China’s broader “gray zone” tactics, which include military drills, cyberattacks and disinformation campaigns targeting Taiwan. The suspected act of sabotage mirrors similar incidents in the Baltic Sea, where Chinese-linked ships were blamed for severing data cables and pipelines. Together, the events highlight China’s undersea warfare strategy and its pursuit of undersea dominance.
From 1982 to 1988, under the strategic vision of then-Chinese People’s Liberation Army (PLA) Navy commander-in-chief Liu Huaqing (劉華清), often regarded as the father of the modern Chinese navy, China developed a three-phase plan for naval growth. Under the plan, the PLA Navy aimed to dominate the waters within the first island chain by 2000, the second island chain by 2020 and deploy a global navy, including aircraft carriers, by 2050. The vision has driven the PLA Navy to steadily invest in bolstering its capabilities across surface, aerial and underwater domains, aspiring to become a “blue-water navy with global influence” by mid-century.
China’s underwater strategy aligns with its blue-water ambitions and broader “two-ocean strategy” aimed at expanding its naval presence in both the Pacific and Indian oceans. The approach emphasizes “far seas operations,” combining control in the South China Sea with “sea denial” in distant waters. Chinese maritime strategist Hu Bo (胡波), director of Peking University’s Center for Maritime Strategy Studies, underscored the importance of two ocean-going fleets, centered on aircraft carriers.
For “near-seas active defense,” China’s strategy of anti-access/area denial is key to restricting foreign access and maneuverability in the South China Sea and surrounding areas. The system integrates advanced missiles, submarines, surface ships, and electronic and underwater warfare tools, creating a layered defense across the first and second island chains. Beyond defense, the capabilities enable Beijing to assert control over disputed territories and potentially launch operations against Taiwan, solidifying its regional dominance.
The PLA Navy commands the world’s third-largest submarine fleet, comprising both conventional and nuclear-powered submarines that support near-sea defense and far-sea operations. The submarines, alongside ballistic missile submarines and uncrewed underwater vehicles (UUVs), play critical roles in securing China’s strategic interests in the Taiwan Strait, South China Sea and Indian Ocean.
The incorporation of UUVs enhances China’s intelligence gathering, surveillance and reconnaissance capabilities, while also supporting anti-submarine warfare, mine detection and sabotage of enemy communications, information or energy infrastructure. With their stealth and ability to operate autonomously in shallow waters or at long standoff distances, UUVs complement China’s submarine fleet by bolstering underwater operations, improving situational awareness, protecting key maritime interests and extending operational reach. That integration further solidifies China’s strategic presence in the Indo-Pacific region.
China’s undersea warfare strategy is a crucial part of its broader efforts to dominate the South China Sea, a region central to global trade and geopolitics. Facilitating more than US$5 trillion in annual trade, the South China Sea is a key maritime artery for vital commodities such as oil, gas and fish, essential for regional energy and food security.
Amid overlapping territorial claims involving Taiwan, the Philippines, Vietnam, Malaysia, Brunei and Indonesia, China has reinforced its dominance through historical assertions and the construction of artificial islands. Since 2009, China has further intensified its militarization of the region, deploying submarines, advanced surveillance technologies and establishing strategic bases to secure its buffer zones and safeguard its ballistic missile submarines bastions.
In a potential conflict with Taiwan, China’s underwater strategy would likely leverage advanced undersea drones and other maritime technologies to assert dominance in the Taiwan Strait. The drones could scout for US submarines, disrupt their operations or launch targeted attacks to divert attention and resources. Additionally, China could flood the region with decoy drones to confuse US and Taiwanese forces, making it harder to distinguish between high-value targets and nonthreatening vessels.
With its proximity to Taiwan and its significant advantage in drone production, China is well-positioned to deploy such autonomous systems effectively, creating a strategic edge in undersea warfare. The use of artificial intelligence-driven navigation and swarming tactics further enhances the potential impact of these technologies.
China’s strategic ambitions in the undersea domain, highlighted by incidents such as the cutting of undersea cables near Taiwan, align closely with its broader maritime and digital goals. Such efforts focus on three interconnected areas: undersea fiber-optic cables, seabed mapping and deep-sea mining.
Central to these initiatives is Beijing’s Digital Silk Road initiative, which seeks to enhance global telecommunications connectivity through cross-border cable networks and transcontinental submarine projects, all designed and controlled by China to expand its influence and infrastructure dominance.
Ocean mapping is pivotal to China’s maritime and military strategy. Detailed hydrographic data are essential for submarine operations, anti-submarine warfare, undersea cable installation and seabed mining, reinforcing both strategic and economic goals. By offering hydrographic services to smaller nations with limited capabilities, Beijing secures access to critical maritime information while extending its geopolitical influence.
However, that approach has triggered sovereignty concerns in nations such as Sri Lanka and the Maldives, where protests have prompted efforts to build local capabilities to safeguard national hydrographic data.
Leveraging technological advancements, Beijing pursues its ambitious undersea goals as outlined in its five-year plans. The initiatives emphasize ocean observation technologies, remote sensing and global monitoring networks, providing critical bathymetric data for undersea warfare. That enables China to extend its reach and control in the Taiwan Strait and the South China Sea, while also supporting the installation of submarine cables, which bolster Beijing’s dominance in the communications and information sectors.
Additionally, the strategy facilitates resource extraction, providing much-needed revenue streams and access to critical minerals essential for digital infrastructure. By asserting physical control over ocean territories, securing data dominance and consolidating resource control, China is redefining strategic spaces in the undersea domain, with far-reaching implications for global security, data privacy and resource competition.
Antonio Graceffo, a China economic analyst who holds a China MBA from Shanghai Jiao Tong University, studies national defense at the American Military University.
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