The East and South China Seas: One Sea, Near Seas, Whose Seas?

China Seas

Editor’s Note: This is part of a short series examining maritime geography and strategic challenges in specific bodies of water, ranging from the Arctic Ocean to the Gulf of Guinea and the South China Sea.

One Sea, Two Seas, Far Seas, Near Seas? For all the attention they receive as contested Indo-Pacific maritime regions, the strategic differences between East and South China Seas do not always get their due. Each of these bodies of water contains land features claimed by the People’s Republic of China and at least one ally or partner of the United States. To Beijing, the East and South China Seas are all part of its “near seas,” and China continues to take steps to assert control over this space as one unified maritime periphery — which we refer to colloquially as China’s “One Sea.” The disputed land features in these seas are small — islands, reefs, and rocks — but the economic, maritime, and security stakes associated with them are large. Countries around the East and South China Seas, however, are not taking China’s actions passively. In their own unique ways that reject the notion of a single “One China Sea,” these countries are adapting and exploring new methods to assert their own maritime rights.

For those who view this region from afar, understanding the differences between the East and South China Seas is an important first step toward addressing the challenges posed by Beijing. Disputes in the East China Sea are primarily bilateral. Japan has expressly denied that China has any legitimate claims to the Senkaku Islands. In the South China Sea, disputes are inherently multilateral because of the large number of claimants and role of the Association of Southeast Asian Nations. It is also important to appreciate the rapidly evolving responses from nations contesting China’s claims, each of which employs unique approaches. In the Philippines, President Ferdinand Marcos Jr. has noted the need for a “paradigm shift” in terms of diplomatic approaches to the disputes — this stark rhetoric contributes to increased tension between Manila and Beijing, with the most recent incidents occurring in March. Vietnam has continued land reclamation activities, but also signed agreements to increase cooperation with the Philippines. Malaysia states that its “position on the South China Sea is consistent and remains unchanged” while quietly resolving some issues with neighbors such as Brunei. In the Taiwan Strait, which sits between the East and South China Seas, tensions between China and Taiwan continue to concern neighbors that could be drawn into a potential conflict. In the long term, understanding each country’s approach will be necessary for fully resolving the disputes. In the near term, U.S. policymakers will need to continue to tailor their approach in a way that acknowledges these differences while recognizing that the United States is not a claimant state.

With all this in mind, we argue that U.S. policymakers should maintain realistic expectations for dispute resolution, while also pushing for the (long overdue) Senate ratification of the U.N. Convention on the Law of Sea. The United States should continue to enable partners to ensure that all nations have access to the East and South China Seas.



East and South China Seas: Parallels

Clear similarities exist between the East and South China Seas. First, the two bodies of water have comparable geographies, and each play a key role in maritime shipping. Both are bound in one direction by mainland China and in the other by the first island chain, a series of archipelagoes extending from Russia’s Kamchatka Peninsula in the northeast down through Japan and Taiwan to the Malay Peninsula in the southwest.

Second, the East and South China Seas are rich in biological and energy resources. Both contain valuable fishing grounds that support the economic growth and food security of East and Southeast Asian countries. According to one estimate, the value of these fisheries is over $7 billion in the East China Sea and more than $15 billion in the South China Sea. In terms of oil and gas resources, the U.S. Energy Information Administration estimates that the hydrocarbon reserves in the East China Sea comprise at least 200 million barrels of oil and up to 2 trillion cubic feet of natural gas. In the South China Sea, the estimate is considerably higher: 11 billion barrels of oil and 190 trillion cubic feet of natural gas. Yet, due to increasing exploitation of their rich resources, the two seas face significant environmental concerns, facing challenges from pollution, natural habitat destruction, and severe depletion of fish stocks. In the South China Sea, coral reef cover is declining at a rate of 16 percent per decade.

Third, the two seas have seen increasing militarization, as countries competing for resources have more assertively enforced their maritime claims. In the South China Sea, this has included nations reclaiming land, constructing artificial islands, building military outposts on land features, conducting intelligence gathering and sovereignty patrols, and engaging in occasional altercations such as the 2014 China-Vietnam oil rig crisis. Although the East China Sea has not seen disputants build military infrastructure on contested land features, waters around the Senkaku Islands (which China calls the Diaoyu Islands) are increasingly the site of patrols by military and paramilitary forces. As tensions continue to simmer over Taiwan — which Beijing views as an inherent part of China — the waters in and around the Taiwan Strait have become stages for frequent presence and deterrence operations with escalatory potential.

“One China Sea”?

From Beijing’s perspective, both the East and South China Seas should be controlled in a unified manner as part of China’s territorial sea. China has employed diverse legal and military means to attain this objective despite longstanding objections and countermeasures from other claimants.

Beijing’s legal tactics to assert control over its maritime periphery have included a selective approach to international maritime law buttressed by Chinese domestic law. In 1992, China’s government passed the Law on the Territorial Sea and the Contiguous Zone of the People’s Republic of China “to exercise its sovereignty over its territorial sea” — defined as encompassing all islands in the East and South China Seas. In 1996, China ratified the U.N. Convention on the Law of the Sea but declared that its own domestic law affirmed its sovereignty over “all its archipelagoes and islands,” including those outlined in the 1992 law. Since China did not agree with the exclusive economic zone provisions of the convention, Beijing also passed a domestic law in 1998 specifying that China “exercises its sovereign rights and jurisdiction over its exclusive economic zone and its continental shelf.” Beijing continues to make claims about “historic rights” to the South China Sea, though most legal scholars agree that these claims are either inconsistent with the convention or undermine international maritime law. After the July 2016 Permanent Court of Arbitration ruling in favor of the Philippines, China issued a white paper outlining an extensive list of reasons why the Chinese government thought the ruling was wrong.

For Beijing, these seas represent critical access to maritime power. The People’s Liberation Army Navy, China Coast Guard, and China Maritime Militia regularly patrol these waters. The world’s 6 busiest container ports are located on the shores of one of these seas, including Shanghai, Ningbo, and Qingdao (East China Sea) and Singapore, Shenzhen, and Guangzhou (South China Sea). Global trade passing through the South China Sea alone each year is worth over 3 trillion dollars, and China continues to drive intra-Asian container traffic despite changes in supply chains after the COVID-19 pandemic.

For many years, China has employed its armed forces to enforce its sovereignty claims and deter foreign military intervention. Beijing has steadily modernized its military and employed a diverse range of tactics in the East China Sea, South China Sea, and Taiwan Strait to intimidate the forces of smaller militaries and complicate U.S. military operations in these areas. According to the U.S. Department of Defense, since the fall of 2021 the Chinese military has exhibited an increasing trend of coercive and risky operational behavior against U.S. and allied military ships and aircraft. Examples from the past year include a Chinese destroyer crossing a U.S. destroyer’s bow at dangerously close distance in the Taiwan Strait and a Chinese fighter’s unsafe and unprofessional intercept of a U.S. bomber flying over the South China Sea.

East versus South China Seas: Divergence

Sovereignty disputes in the East China Sea are primarily bilateral. The argument between China and Japan over the Senkaku Islands is largely distinct from tensions between China and Taiwan although the dividing line between the two disputes has begun to blur. In the South China Sea, the issue is fundamentally multilateral because of the important role of the Association of Southeast Asian Nations, even if individual features may be disputes bilaterally or trilaterally.

In the bilateral disputes between China and Japan, tensions have alternated between periods of restraint and escalatory conduct. For example, during the administration of Junichiro Koizumi in Japan (2001–2006), Japan strengthened its claims and China showed restraint, as described by Andrew Taffer. Later, between 2008 and 2010,  Beijing undertook a more coercive strategy prompted, in part, by an incident between a Chinese trawler and Japan Coast Guard ship. The latest escalatory wave began in 2020, as China Coast Guard vessels moved from “normalizing” operations around the islands to attempting to “exercise control” by patrolling these waters without interruption. In 2022, the China Coast Guard once again increased the regularity of its presence, conducting operations for an unprecedented 336 days.

The Taiwan Strait: It’s Complicated

While East China Sea disputes remain primarily bilateral (with the potential for U.S. intervention), the status of Taiwan has complicated national security planning for adjacent countries. A major escalation in the strait followed then-U.S. House of Representatives Speaker Nancy Pelosi’s 2022 visit to Taiwan, which received strong opposition from Beijingcontributing to what some have called the “Fourth Taiwan Strait Crisis.” Beijing responded to the Pelosi visit by having the People’s Liberation Army engage in a series of major exercises that included missile overflights of Taiwan with five ballistic missiles landing in Japan’s exclusive economic zone. Although the military exercises died down after several days, China’s armed forces continue to conduct frequent patrols across the Taiwan Strait median line and in other waters and airspace near Taiwan. In February, the China Coast Guard boarded a sightseeing cruise in the vicinity of the island of Kinmen (Jinmen) within days of an incident involving the Taiwan Coast Guard and a Chinese fishing vessel.

Amid growing regional security concerns, Japan released three major strategic documents in December 2022 that laid the groundwork for an unprecedented increase in military spending and the development of offensive capabilities. These documents — Japan’s National Security Strategy, National Defense Strategy, and Defense Buildup Program — have significant implications for a Senkaku Islands contingency, as well as implications for any potential conflicts in the Taiwan Strait. These policies build upon a line of public rhetoric first seen in Japan’s 2021 defense white paper in which Tokyo links the security of Taiwan to Japan’s own security. Tokyo’s greenlighting of increased defense spending and commitment to purchase “stand-off defense capability” has likely affected Beijing’s calculus.

South China Sea disputes are largely multilateral because Malaysia, the Philippines, Vietnam, and Brunei are all Association of Southeast Asian Nations member states. Three or more parties claim sovereignty over many of the land features in the South China Sea. China, Taiwan, and Vietnam contest sovereignty over the Paracel Islands in the sea’s north and the Spratly Islands in its south. The Philippines, Malaysia, and Brunei also claim sovereignty over some of the Spratly Islands. Brunei, considered the “quietest claimant nation” because it does not engage in public debates on the disputes, has abandoned some territorial claims with Malaysia in the interests of joint development between the two countries. Taiwan has its own claims in the South China Sea, which grew out of policies prior to 1949, when the Nationalist Party (Kuomintang) still controlled mainland China.

Unlike the Senkaku Islands, which are uninhabited, a distinguishing feature of the South China Sea is that all sovereignty claimants (except Brunei) militarily occupy multiple disputed land features. South China Sea claimants have pursued multilateral mechanisms — via the Association of Southeast Asian Nations, U.N. Convention on the Law of the Sea, and the Permanent Court of Arbitration — to manage territorial sovereignty disputes. Yet, those multilateral efforts have not stopped the military build-up. Most countries’ military footprints are relatively austere, but China’s large-scale land reclamation activities transformed several features of the disputed Spratly Islands into bases with military capabilities far outstripping the facilities of other claimants. Building military facilities could be viewed as inconsistent with the China-Association of Southeast Asian Nations Declaration of Conduct, which was agreed to in 2002. The Declaration of Conduct, while technically non-binding and meant to lead to an actual Code of Conduct, expressly stated that claimants should “exercise self-restraint” by not inhabiting features.

China’s military efforts to consolidate anti-ship, anti-air, and other capabilities on its Spratly outposts has not deterred other states, such as the Philippines, from their own claims. Despite significant differences in combat power, confrontations have recently occurred around Second Thomas Shoal (a submerged reef in the Spratly Islands) and Scarborough Shoal (a rock in the eastern part of the South China Sea). In December 2023, China Coast Guard cutters used water cannons against Philippine resupply vessels at Second Thomas Shoal and rammed one of the vessels. Tensions around those land features continue to simmer, and in March, a collision between “Chinese and Philippine coast guard vessels” resulted in injuries to four Filipino crew members.

Conclusion: Several Seas, Many Problems, New Solutions?

China does not have one “best strategy” in its near seas, but employs several interrelated strategies: establish de facto control over territory, bargain when possible, escalate when necessary, accommodate when it serves other strategic purposes, and shape (or ignore) regional and international institutions involved in dispute resolution. For those who follow the South China Sea, it feels like we are watching the movie Groundhog Day, with the same issues being re-hashed year after year. The China-Association of Southeast Asian Nations Declaration of Conduct is supposed to lead to a formal Code of Conduct in the South China Sea, but negotiations continue to be bogged down by significant disagreements over its purpose and whether decisions would be binding. Critics of the negotiations argue that China is deliberately slowing the process to consolidate its military gains. But China might not be the only problem. Over 82 percent of Southeast Asians believe that “[the Association of Southeast Asian Nations] is slow and ineffective,” based on a survey conducted by the Association of Southeast Asian Nations Studies Centre at the ISEAS-Yusof Ishak Institute in Singapore.

The United States is not a claimant state, and because of the intractability of the underlying maritime and territorial disputes, U.S. policymakers should expect more déjà vu in the South China Sea. Many policy recommendations have already been implemented, such as increasing partner capacity (for example U.S. donations of patrol vessels to the Philippines) and enhancing regional maritime domain awareness. Other key steps, such as U.S. Senate ratification of the U.N. Convention on the Law of the Sea, have yet to occur. For Washington, supporting partners with the most at stake allows those countries to exercise their own agency. Japan has updated its defense policies because of concerns about the risks of conflict in the Taiwan Strait, as well as other regional issues. Vietnam has deployed its own vessels to monitor China Coast Guard activities in the South China Sea. In January, the Philippines and Vietnam signed two memorandums of understanding to “enhance coordination on maritime issues,” illustrating that it is up to claimant states to figure out how to resolve these disputes. The United States can increase assistance to those partners, as the current administration has emphasized, but cannot solve the disputes themselves.

Yet, enabling partners and allies provides evidence of the U.S. commitment to the rules-based international order and highlights the potential of minilateral solutions. Beijing often criticizes countries, such as Japan, of “ganging up to form cliques and fanning bloc confrontation” against China. But this narrative places too much focus on antiquated Cold War narratives and allows too little acknowledgement of the frustrations of those nations around China’s expansive definitions of what constitutes “Chinese territory.” Enduring U.S. rhetorical and material support to partners may, at times, increase tensions around specific hot spots, such as Taiwan or Second Thomas Shoal. But occasional tensions are preferable to the costs of inaction. Beijing’s incremental approach to strengthen the People’s Liberation Army and Coast Guard posture in the South China Sea has allowed China to overwhelm the military and law enforcement capacity of other claimants. In the East China Sea, China’s patrols risk more incidents, but the close proximity to Taiwan further complicates decision-making for Japan, the United States, and Taiwan. Living up to U.S. rhetoric on maintaining the rules-based international order means reinforcing partners and institutions that allow all nations access to the East and South China Seas and contest Beijing’s efforts to consolidate these seas into “One China Sea.”



April A. Herlevi is a senior research scientist at the Center for Naval Analyses at the nonprofit research organization CNA and a non-resident fellow at the National Bureau of Asian Research. She was in Beijing in 2010 when China signaled its desire to build facilities in the South China Sea. From 2020 to 2022, she lived in Okinawa in the East China Sea and watched firsthand as Japan’s defense posture changed. She now resides on O‘ahu in the Hawaiian Islands and analyzes China’s foreign policy in its near and far seas.

Brian Waidelich is a research scientist at CNA’s China and Indo-Pacific Security Affairs Division and president of the Yokosuka Council on Asia-Pacific Studies. His research interests include politics and security in East Asia, with a focus on maritime and space issues involving China and Japan.

The authors’ opinions are theirs alone and do not represent the opinions of the Center for Naval Analyses or any of its sponsors.

Image: Rumsey Map Collection