China’s Maritime Great Wall in the South and East China Seas

Recent Features


China’s Maritime Great Wall in the South and East China Seas

China is building a maritime cordon sanitaire.

China’s Maritime Great Wall in the South and East China Seas
Credit: U.S. Navy photo by Mass Communication Specialist 2nd Class Declan Barnes/Released

While the Silk Road strategy could ensure China’s energy security within a generation and effectively circumvent U.S. command of the global maritime commons, it does not shield China’s eastern seaboard from the threat of a U.S. naval attack.  As a land power, the Middle Kingdom does not have to worry about the unlikely possibility of a conventional American assault on the mainland via amphibious landing by sea, parachuting troops by air, or an expeditionary force marching through a land invasion route. What it is vulnerable to is U.S. control of the seas outside China’s 12-nautical mile maritime boundaries. From such an over-the-horizon maritime vantage point, the U.S. Navy has the capability to cripple Chinese infrastructure along the eastern seaboard by long range shelling, missiles, and unmanned aerial bombing.

To address this weakness, in addition to modernizing and expanding its land-based anti-access/area denial capabilities, China is systematically establishing and demarcating a maritime equivalent of the Great Wall — a cordon sanitaire running from the South China Sea through the East China Sea to the Yellow Sea.

Taiwan and the Daioyu/Senkaku Islands

Geostrategically, Taiwan looms large in China’s effort to establish a maritime cordon sanitaire.  The island straddles the passageway connecting the East China Sea to the South China Sea and its southern tip overlooks the Luzon Strait (which connects the Philippine Sea and Pacific Ocean to the South China Sea).  Should Beijing succeed in “reunifying” Taiwan, the island will serve as China’s sentinel guarding a maritime arc between the southern tip of Japan’s Ryukyu island chain and northern Philippines.

Also in this area are the five uninhabited islands known as the Diaoyu Islands in China and the Senkakus in Japan. Taiwan, China, and Japan also claim sovereignty over these East China Sea islands, which are located about 200 kilometers northeast of Taiwan and southwest of the Ryukyu island chain (of which Okinawa, which hosts the bulk of U.S. forces in Japan, is the most important). Japan, which exercised sovereignty over the Senkakus from the 1895 takeover of Taiwan to the end of World War II, regained administrative control over the island chain from the United States in 1972, as the last vestige of American military control of Japanese territory came to an end. The strategic importance to Beijing of the Diaoyu/Senkaku Islands is that they help demarcate Taiwan’s and China’s maritime boundaries, which in turn is critical to establishing China’s cordon sanitaire.

In the absence of a resolution of the dispute, however, Beijing is likely to occupy the islands following a potential reunification of Taiwan, the U.S.-Japan mutual defense treaty notwithstanding. China would be emboldened to take such drastic action by not being vulnerable to an energy embargo led by the United States. Given China’s expected naval dominance in the East China Sea by 2035, a Japanese military effort to recover the seized islands is unlikely. Moreover, the likelihood of American military intervention is questionable as well, despite numerous assurances from U.S. officials.

Article V of the Japan-U.S. Security Treaty states: “[E]ach Party recognizes that an armed attack against either Party in the territories under the administration of Japan would be dangerous to its own safety and declares it would act to meet the common danger.”  This clause, far from signaling an iron-clad American commitment to defend Japan, reflects American caution against being drawn into a military conflict on behalf of its ally.

First, an attack on Japan is not characterized as the equivalent of an attack on the United States, thereby implicitly differentiating its impact in shaping a response. Second, there is no specific reference to the option of military retaliation, thereby implicitly suggesting that an armed attack on Japan would not necessarily trigger a kinetic reaction. In sharp contrast, the comparable Article V provisions of the NATO Treaty convey a far more muscular American commitment to European defense: an armed attack on a NATO ally would be considered an armed attack on the United States, and the option of a military response is explicit.

The Penumbra of the Nine-Dash Line

The most challenging part of Beijing’s effort to establish a maritime cordon sanitaire is gaining acquiescence to the use of the so-called nine-dash line as at least a de facto maritime boundary in the South China Sea. The nine-dash line (originally eleven-dash line) was introduced in official maps in 1948 by the Republic of China as part of the KMT-led government’s effort to demarcate China’s boundaries. At the time of its establishment in 1949, the People’s Republic of China inherited this demarcation of the South China Sea. Both Taipei and Beijing have continued to insist on this line as the proper basis for delineation of China’s maritime claims in the South China Sea.

Beijing is gradually reinforcing its claims to various islands and rocks in the South China Sea that fall within the nine-dash line through a program of artificially extending the islands (mainly through reclamation involving excavation and landfills) and building dual-use features such as air strips, docks, radar stations, and lighthouses. China has also offered bilateral negotiations to each of the countries with which it has overlapping claims in the South China Seas: Philippines, Malaysia, Brunei, and Vietnam. The United States, however, has rejected the use of the nine-dash line as the basis of demarcating China’s maritime boundary in the South China Sea. Ultimately, China will have to rely on the combined weight of its economic and naval power in East Asia to achieve de facto acceptance of China’s maritime boundaries.


It will take decades before China’s maritime cordon sanitaire becomes a fait accompli. The limited objective is for the Chinese navy to leverage its on-shore protective umbrella to gain local superiority over any U.S. naval force that might be mobilized against it. It will take time, most likely a generation, to achieve this objective.

China’s advantage is that it does not have, nor does it seek, the responsibility for controlling the global maritime commons, and, therefore, Beijing can concentrate substantially its entire naval fleet on ensuring that it controls what it considers to be territorial waters within the Middle Kingdom’s maritime Great Wall. The U.S. Navy, by contrast, has the responsibility of controlling the global maritime commons given the unique status of the United States as the sole global power. Consequently, the U.S. Navy can only allocate a part of the fleet to patrol what it considers to be international waters off the coast of China.

Over the next 20 years, China appears determined to build a navy that is qualitatively adequate and quantitatively significantly larger in size to deter any U.S. naval force that is likely to be arrayed against it in the cordon sanitaire. If conflict is to be avoided, China and the United States will have to craft a modus vivendi with respect to innocent passage and peaceful navigation (but short of freedom of navigation) through the cordon sanitaire in the South China, East China, and Yellow Seas.

Samir Tata is the founder of International Political Risk Analytics, based in Reston, VA.  He has previously served as an intelligence analyst with the National Geospatial-Intelligence Agency, a staff assistant to Senator Dianne Feinstein, and a research associate with Middle East Institute, Atlantic Council, and National Defense University.