China May Turn South China Sea Into AI‐Triggered Mine Zone

According to the report, at least 11 nuclear attack submarines (SSNs)-including USS Seawolf, USS Asheville, and USS Minnesota-two guided-missile submarines (SSGNs), USS Michigan and USS Florida, and one ballistic-missile submarine (SSBN), USS Louisiana operated in the region, supported by tenders USS Frank Cable and USS Emory S. Land.

Those submarines are likely tasked with shadowing China's SSBNs, which form the sea-based leg of its nuclear deterrent, providing a survivable second-strike capability.

China's six Type 094 SSBNs are the centerpiece of its sea-based nuclear deterrent. Each Type 094 SSBN carries 12 submarine-launched ballistic missiles (SLBMs), performing near-continuous patrols in the South China Sea, with one unit constantly at sea .

However, China's SSBNs may have significant limitations. Ryan Martinson, citing Chinese military sources in a June 2025 Center for International Maritime Security (CIMSEC) article , notes that China's submarines are relatively noisy and are vulnerable to the US's undersea detection network, presenting a serious threat to China's undersea nuclear deterrent, increasing China's vulnerability to a sudden attack.

China's bastion strategy keeps its SSBNs operating in the South China Sea, shielded by fortified islands, aircraft, warships, and other submarines. But this confinement to a relatively small area makes them easier to detect compared to open-ocean patrols.

The limited range of China's JL-2 submarine-launched ballistic missiles (SLBMs), which is only 8,000–9,000 kilometers, also confines it to this bastion approach. From the South China Sea, the missiles cannot reliably hit the US mainland, forcing China's SSBNs to stay close to home rather than risk vulnerable transits into the wider Pacific.

Any breakout into the Pacific would mean transiting chokepoints like the Miyako Strait or Bashi Channel, where US and allied forces could intercept them.

China hopes to offset these constraints with the new JL-3 SLBM, which may overcome these limitations. With a range of over 9,000 kilometers, it could enable China's SSBNs to hit the US mainland from its South China Sea bastions.

Despite these advancements, China's South China Sea bastion may still be incomplete, with coverage limited to a line stretching from Hainan, the Paracels, and the Spratlys, leaving out most of the northern part of the semi-enclosed body of water.

China lacks a northern outpost in the South China Sea, with the disputed Scarborough Shoal being the most suitable candidate for such a location. Should China build over and fortify Scarborough Shoal as it has done with its other occupied features in the Paracels and Spratlys, it would enable a complete triangulation of the South China Sea from Hainan and the Paracels and Spratlys, with Scarborough Shoal forming the northernmost tip of China's SSBN bastion.

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While China has de facto control of Scarborough Shoal since 2012, it has not initiated island-building activities on that disputed feature. The Philippine government has consistently stressed that any island-building on Scarborough Shoal would be a“red line,” even as the US, its only treaty ally and main security guarantor, has excluded it from 1951 Mutual Defense Treaty (MDT) coverage .

Despite the US excluding Scarborough Shoal from 1951 MDT coverage, the US, Philippines, and other allies have conducted FONOPS near the contested area at a relatively high tempo, with the presence of US and allied military assets possibly deterring China from tightening its hold on the disputed feature.

Furthermore, the Philippines has recently acquired BrahMos supersonic cruise missiles from India, with plans to purchase additional units. The Philippines' new BrahMos missiles can't reach Hainan or mainland China - but they don't need to. Scarborough Shoal, just 230 kilometers from Luzon, is a fixed target easily within its 290-kilometer range. This localized deterrence shapes China's calculus.

Such a situation may prevent China from using its sea-based nuclear deterrent as a strategic backstop against US and allied intervention during a Taiwan contingency. China could opt to use its SSBNs as part of larger nuclear threats to deter US and allied intervention, push Taiwan to surrender, or force negotiations if Chinese conventional forces falter.

Even as China doubles down on turning the Paracels into a submarine killing field, its northern flank remains a hole the US and its allies can exploit.

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