South China Sea: US-China Simultaneous Military
In early 2026, the U.S. and China simultaneously deployed large-scale military exercises in the South China Sea, with the risk of accidental clashes reaching its highest level since the Cold War. This tension is accelerating a structural shift in regional security involving Japan, the Philippines, and Taiwan, threatening freedom of navigation in the South China Sea, a vital artery of the global economy.
── Understand in 3 points ─────────
- • From January to March 2026, the People's Liberation Army Navy (PLAN) conducted its largest-ever live-fire exercise in the South China Sea, involving over 40 vessels, including the aircraft carrier "Fujian."
- • The U.S. Navy, centered on the 7th Fleet, conducted "Freedom Edge" exercises in the Philippine Sea and South China Sea, deploying two carrier strike groups (Nimitz-class "Carl Vinson" and Gerald R. Ford-class "Ford").
- • The Chinese Foreign Ministry stated that "extra-regional countries are disrupting regional stability." The U.S. Department of State countered that "freedom of navigation is not negotiable."
── NOW PATTERN ─────────
In the South China Sea, the "spiral of conflict" has entered a self-reinforcing loop. A structure is solidifying where one side's exercise prompts a counter-exercise from the other, which in turn justifies further escalation. Simultaneously, "alliance strains" are running through the respective alliance networks of the U.S. and China, accumulating risks of "overreach of power" for both sides.
── Probability and Response ──────
🟡 Base 55% — China Coast Guard patrol frequency and behavior patterns, U.S. Navy FONOP frequency and scale, level of interference with Philippine resupply activities (escalation from water cannons to physical collision), frequency of U.S.-China military hotline use
🟢 Optimistic 20% — Setting of a Trump-Xi Jinping summit (whether the South China Sea is on the agenda), signs of China's concession on legal enforceability in COC negotiations, resumption/expansion of U.S.-China military dialogue channels, temporary halt of China's artificial island construction activities
🔴 Pessimistic 25% — U.S.-China military hotline outage/delay, changes in China Coast Guard rules of engagement (expanded application of the 2021 Coast Guard Law), intensity of physical obstruction to Philippine resupply activities at Second Thomas Shoal, deployment of new weapons (e.g., HQ-9B) to artificial islands, increase in cyberattacks
📡 The Signal — What Happened
Why it matters: In early 2026, the U.S. and China simultaneously deployed large-scale military exercises in the South China Sea, with the risk of accidental clashes reaching its highest level since the Cold War. This tension is accelerating a structural shift in regional security involving Japan, the Philippines, and Taiwan, threatening freedom of navigation in the South China Sea, a vital artery of the global economy.
- Military Developments — From January to March 2026, the People's Liberation Army Navy (PLAN) conducted its largest-ever live-fire exercise in the South China Sea, involving over 40 vessels, including the aircraft carrier "Fujian."
- Military Developments — The U.S. Navy, centered on the 7th Fleet, conducted "Freedom Edge" exercises in the Philippine Sea and South China Sea, deploying two carrier strike groups (Nimitz-class "Carl Vinson" and Gerald R. Ford-class "Ford").
- Diplomacy — The Chinese Foreign Ministry stated that "extra-regional countries are disrupting regional stability." The U.S. Department of State countered that "freedom of navigation is not negotiable."
- Alliance Relations — Joint patrols by Japan, the U.S., and the Philippines became regularized from February 2026. A Japan Maritime Self-Defense Force Soryu-class submarine made its first port call at Subic Bay in the Philippines.
- Economic Impact — Annual trade value passing through the South China Sea is approximately $5.3 trillion (about 30% of global trade). Maritime insurance rates rose by 15-20% compared to 2025.
- Territorial Issues — China confirmed new runway extension work on Mischief Reef and Subi Reef in the Spratly Islands. Satellite images also revealed the addition of hangars.
- Military Technology — China deployed an improved version of the DF-26B (carrier-killer missile) along the South China Sea coast. With a range of 4,000 km, U.S. military bases in Japan are also within range.
- International Law — Ten years have passed since the 2016 South China Sea arbitration ruling (which rejected China's nine-dash line), but China has consistently rejected the ruling, expanding its effective control.
- Regional Reaction — At the ASEAN Foreign Ministers' Meeting, negotiations for a Code of Conduct (COC) in the South China Sea set a target for conclusion in 2026, but disagreements persist over its legal enforceability.
- Impact on Japan — The Japanese government decided to strengthen anti-ship missile units on Ishigaki Island and Miyako Island for the defense of the Nansei Islands. The 2026 defense budget is a record 7.9 trillion yen.
- Energy — The South China Sea seabed is estimated to hold 11 billion barrels of oil and 190 trillion cubic feet of natural gas. China National Offshore Oil Corporation (CNOOC) began new drilling in disputed waters.
- Cyber and Information Warfare — U.S. Cyber Command confirmed activities by "Volt Typhoon," a Chinese-backed hacker group targeting Philippine military networks, warning of intrusions into military communication infrastructure.
The South China Sea is the geopolitical fault line of the 21st century. To understand the tensions in this region, one must decipher the structural changes over the past half-century.
**Cold War Vacuum and China's Advance (1970s-1990s)**
The South China Sea territorial dispute dates back to the 1974 Battle of the Paracel Islands (a military clash between China and Vietnam). During the Cold War, the U.S. was in withdrawal mode after the Vietnam War, and its involvement in this area was limited. Exploiting this "power vacuum," China engaged in a naval clash with the Vietnamese Navy at Johnson South Reef in the Spratly Islands in 1988, bringing several atolls under its effective control. In 1995, China built structures on Mischief Reef, which the Philippines claims, accumulating faits accomplis.
**Nine-Dash Line and "Maritime Power" Strategy (2000s-2010s)**
In 2009, China submitted a map including the "nine-dash line" to the UN, officially asserting historical rights over almost the entire South China Sea. This was linked to President Xi Jinping's "maritime power" vision. From 2013 onwards, China began large-scale artificial island construction in the Spratly Islands. Fiery Cross Reef, Subi Reef, and Mischief Reef were equipped with 3,000-meter runways, radar facilities, and anti-aircraft missiles, becoming de facto military fortresses.
The Obama administration intensified its involvement in 2010 when Secretary of State Hillary Clinton declared that "freedom of navigation in the South China Sea is a U.S. national interest." However, the U.S. response at this time was limited to diplomatic protests and sporadic "Freedom of Navigation Operations (FONOPs)," and it did not physically prevent China's artificial island construction.
**Arbitration Ruling and the Limits of the "Rule of Law" (2016)**
In July 2016, the Permanent Court of Arbitration in The Hague issued a landmark ruling based on a Philippine petition, stating that China's nine-dash line had no legal basis. However, China dismissed it as "a piece of paper" and completely ignored the ruling. At this moment, the limits of international law for dispute resolution were exposed. Legal victory could not change military reality.
**Escalation of U.S.-China Strategic Competition (2017-2025)**
The first Trump administration initiated a trade war with China and increased the frequency of FONOPs in the South China Sea. The Biden administration developed this into an "integrated deterrence" strategy, establishing AUKUS (a security framework between the U.S., UK, and Australia), strengthening Japan-U.S.-Philippines trilateral cooperation, and expanding the Enhanced Defense Cooperation Agreement (EDCA) with the Philippines.
Meanwhile, China deepened its "gray zone strategy." It deployed the China Coast Guard and maritime militia rather than the navy, continuously exerting pressure below the threshold of military conflict. By 2023, water cannon attacks and laser illuminations against Philippine resupply vessels became routine. In 2024, an incident occurred at Second Thomas Shoal where Philippine marines were injured.
**2026: Why Tensions Are Peaking Now**
The situation in 2026 is critically different from the past because three structural changes are occurring simultaneously. First, China's military power is approaching the level of a "peer competitor." The operationalization of the aircraft carrier "Fujian," the mass deployment of DF-26B missiles, and the mass production of Type 055 destroyers are narrowing the qualitative advantage of the U.S. military. Second, the unpredictable diplomatic style of a second Trump administration is amplifying the anxieties of allies, prompting Japan and the Philippines to strengthen their own defense capabilities. Third, the linkage with the Taiwan issue is intensifying. The establishment of military presence in the South China Sea is positioned as part of an "A2/AD (Anti-Access/Area Denial)" strategy to prevent U.S. military access in the event of a Taiwan contingency.
These three changes combine, and the cycle of exercises and counter-exercises has entered a self-reinforcing loop. This is the structural mechanism of the "spiral of conflict."
The delta: The turning point in 2026 is that U.S.-China military exercises began to take on the character of "preparation for actual combat" rather than "demonstrative deterrence." China deployed the aircraft carrier "Fujian" for the first time in a combat-level exercise, and the U.S. responded with its largest post-Cold War deployment of two carrier strike groups simultaneously. This is a signal that both sides have begun to recognize that "the other side is serious," meaning that the threshold for accidental clashes is structurally decreasing.
🔍 Between the Lines — What the News Isn't Saying
The essence of this crisis, officially described as a conflict between "freedom of navigation" and "sovereignty defense," is actually a dress rehearsal for a Taiwan contingency. For China, establishing a military presence in the South China Sea is nothing less than building an "A2/AD corridor" to prevent U.S. military access during a Taiwan invasion. The U.S. deploying two carrier strike groups simultaneously also strongly implies a stress test of "whether China can be contained in a Taiwan contingency." Neither government publicly discusses this context, but all military actions are planned on the premise of this "Taiwan factor." In other words, what we are seeing in the South China Sea is superficially a territorial dispute, but in reality, it is the frontline of U.S.-China strategic positioning over Taiwan, looking towards 2027.
NOW PATTERN
Spiral of Conflict × Alliance Strain × Overreach of Power
In the South China Sea, the "spiral of conflict" has entered a self-reinforcing loop. A structure is solidifying where one side's exercise prompts a counter-exercise from the other, which in turn justifies further escalation. Simultaneously, "alliance strains" are running through the respective alliance networks of the U.S. and China, accumulating risks of "overreach of power" for both sides.
Intersection of Dynamics
These three dynamics — the spiral of conflict, alliance strain, and overreach of power — do not operate independently but **form a "negative resonance" that mutually reinforces each other.**
As the spiral of conflict accelerates escalation, allies' anxieties about "will we truly be protected?" intensify, deepening alliance strains. As alliance strains deepen, the U.S. is forced to deploy a larger military presence to demonstrate alliance credibility, leading to an overreach of power. When resources are dispersed due to overreach of power, responses in various areas become insufficient, creating an incentive for the opposing side to "test," further accelerating the spiral of conflict.
This triangular resonance structure is particularly dangerous because **cutting off any one side will be compensated by the other two.** For example, if the U.S. reduces its military presence for de-escalation (resolving overreach), allied anxieties will increase (expanding strains), giving China a pretext to intensify pressure (accelerating the spiral). Conversely, if China compromises and agrees to a code of conduct (slowing the spiral), domestic nationalism will criticize it as "weak," damaging the regime's legitimacy.
This structure suggests that tensions in the South China Sea cannot be resolved by mere diplomatic management; they will **persist unless there is a structural transformation where all three dynamics are resolved simultaneously (e.g., a grand bargain between the U.S. and China, or the establishment of a new regional security architecture).** And such a structural transformation is extremely difficult in the current political environment. Therefore, the most realistic scenario is the continuation of "managed tension," but the question is how long this "management" can last as the spiral of conflict continues to lower the threshold for accidental clashes.
📚 Pattern History
1914: Outbreak of World War I — Chain Escalation from the Sarajevo Incident
Spiral of Conflict
Structural similarity to the present: Automatic alliance clauses and the speed of military mobilization eliminated room for political judgment. An accidental trigger (assassination) transformed a structurally prepared conflict into a full-scale war. In the current South China Sea, the automatic activation scenario of the U.S.-Philippines Mutual Defense Treaty carries a similar risk.
1962: Cuban Missile Crisis — U.S.-Soviet Nuclear Brinkmanship
Spiral of Conflict + Overreach of Power
Structural similarity to the present: The Soviet deployment of missiles to Cuba (overreach) led to a U.S. naval blockade, creating a 13-day nuclear war crisis. De-escalation was ultimately achieved through back-channel diplomacy (secret negotiations between Robert Kennedy and Soviet Ambassador Dobrynin). Lesson: Since "weakness" cannot be shown through official channels, secret dialogue routes are essential. It is unclear whether such back channels are functioning between the U.S. and China today.
2001: Hainan Island Incident — Mid-air Collision Between U.S. Reconnaissance Plane and Chinese Fighter Jet
Spiral of Conflict
Structural similarity to the present: A U.S. EP-3 reconnaissance aircraft and a Chinese J-8 fighter jet collided in mid-air over the South China Sea, killing the Chinese pilot. The U.S. aircraft made an emergency landing on Hainan Island, and its 24 crew members were detained for 11 days. Both countries claimed "the other side was at fault," escalating into a diplomatic crisis. It was eventually resolved with a U.S. expression of "very sorry," but it served as a precedent showing how quickly an accidental contact can escalate.
1988: Spratly Islands Naval Battle (Johnson South Reef Skirmish) — Military Clash Between China and Vietnam
Spiral of Conflict + Overreach of Power
Structural similarity to the present: The Chinese Navy attacked a Vietnamese transport ship, killing over 64 Vietnamese soldiers. China occupied six atolls. This incident proved that the use of military force in the South China Sea directly leads to territorial expansion. Vietnam, having lost its patron with the collapse of the Soviet Union, could not retaliate. An example where "absence of alliance" led to invasion.
2012: Scarborough Shoal Incident — China's Seizure of Effective Control from the Philippines
Alliance Strain
Structural similarity to the present: The Philippine Navy and China Marine Surveillance confronted each other for two months. A "simultaneous withdrawal" was agreed upon through U.S. mediation, but China did not withdraw and established effective control. The Philippines felt "betrayed by the U.S.," which became a precursor to President Duterte's pro-China stance. This incident showed what happens when an ally feels "the U.S. is all talk."
Patterns Revealed by History
Historical precedents consistently demonstrate the following three lessons:
First, **the competition to expand military presence structurally increases the risk of unintended contact incidents.** What 1914, 2001, and the current South China Sea have in common is the simple physical fact that close deployment of military forces raises the probability of an "accidental trigger."
Second, **the moment alliance credibility is doubted, the opposing side's risk appetite skyrockets.** Scarborough Shoal (2012) and the Spratly Islands Naval Battle (1988) show that military faits accomplis are created when it is perceived that there is "no backing." This means that maintaining the credibility of the current U.S.-Philippines and Japan-U.S. alliances is the cornerstone of deterrence.
Third, **de-escalation requires an "exit that saves face."** The Cuban Missile Crisis was resolved through back channels and secret compromises (missile withdrawal from Turkey in exchange). Political leaders cannot back down unless both sides can publicly claim "victory." In the current South China Sea, such a "face-saving framework for compromise" does not exist. This is one of the structural reasons why the spiral cannot be stopped.
🔮 Next Scenarios
**Continuation of "Managed Tension" — Conflict Avoided, But Spiral Unabated** The most probable scenario is the continuation of "managed tension," where both the U.S. and China intentionally avoid military conflict while the competition to expand military presence persists. China will continue its "gray zone strategy," primarily using the China Coast Guard and maritime militia to exert pressure below the threshold of military conflict. Interference with Philippine resupply activities (water cannons, laser illumination, physical blocking) will become routine but will not escalate to lethal force. The Chinese military will continue to develop military infrastructure on artificial islands, with the runway extension on Mischief Reef completed by the end of 2026. The U.S. will conduct over 15 FONOPs annually and regularize Japan-U.S.-Philippines trilateral joint patrols on a monthly basis. However, the "transactional diplomacy" of a Trump administration will make it difficult to maintain a consistent strategy in the South China Sea, and policy fluctuations will increase allied anxieties. ASEAN Code of Conduct (COC) negotiations will formally progress but are likely to remain at the level of a non-legally binding "gentlemen's agreement." China will use COC negotiations as a diplomatic alibi to show "dialogue" but will not halt the expansion of its effective control. The biggest risk in this scenario is the unpredictable limit of "management." In the event of an accidental contact incident (pilot near-miss, vessel collision), in the age of social media and 24-hour news, public opinion may demand "retaliation" before political leaders can make de-escalation judgments.
Implications for Investment/Action: China Coast Guard patrol frequency and behavior patterns, U.S. Navy FONOP frequency and scale, level of interference with Philippine resupply activities (escalation from water cannons to physical collision), frequency of U.S.-China military hotline use
**U.S.-China Grand Bargain — "Freeze" Agreement in the South China Sea** A scenario where the U.S. and China achieve an unexpected diplomatic breakthrough, reaching an agreement to effectively "freeze" the status quo in the South China Sea. President Trump's transactional diplomatic style paradoxically enables this major agreement. This scenario has three prerequisites. First, a Trump administration leverages South China Sea tensions as a bargaining chip to initiate comprehensive negotiations on trade issues (tariffs, market access). Second, the Xi Jinping administration prioritizes diplomatic stability in response to a slowing domestic economy (real estate crisis, youth unemployment). Third, some accidental incident acts as a "warning," providing both countries with an incentive to compromise (similar to the effect of the Cuban Missile Crisis). The core of the agreement would be China accepting a "freeze on additional militarization" of existing artificial islands, and the U.S. reducing the frequency of FONOPs as a "quiet understanding." It would function as an implicit diplomatic understanding rather than a legal document. The ASEAN Code of Conduct could potentially be used as a "framework." However, even in this scenario, the fundamental territorial issues would not be resolved, and it would only be a "pause" in tensions. The structure for re-escalation would remain intact with the next change in administration or international environment.
Implications for Investment/Action: Setting of a Trump-Xi Jinping summit (whether the South China Sea is on the agenda), signs of China's concession on legal enforceability in COC negotiations, resumption/expansion of U.S.-China military dialogue channels, temporary halt of China's artificial island construction activities
**Accidental Military Clash — A "Mini Hainan Island Incident" Occurs** A scenario where an accidental military clash occurs in the South China Sea, fundamentally altering the regional security environment. The scale of the clash would be limited (a few to dozens of casualties), but the political and economic impact would be immense. There are three most probable clash scenarios. First, a mid-air close encounter between U.S. and Chinese military aircraft (fighter jets, reconnaissance planes) escalates to physical contact (a repeat of the 2001 Hainan Island Incident). Second, the China Coast Guard resorts to lethal force against Philippine vessels (occurring while attempting to completely obstruct resupply activities at Second Thomas Shoal). Third, U.S. and Chinese naval vessels approach abnormally close during exercises, and defensive measures (warning shots, ECM use) escalate. If a clash occurs, the first 72 hours will be decisive. Leaders of both countries will face public demands for "retaliation" on social media, rapidly narrowing de-escalation options. Especially for the Xi Jinping administration, a narrative of "being attacked by a foreign military and backing down" would fundamentally shake the regime's legitimacy, necessitating some form of "retaliatory measure." Economic impacts would be immediate. Maritime insurance rates in the South China Sea would skyrocket several times over, forcing some merchant ships to reroute. The Japanese Yen and Chinese Yuan would fluctuate, and Asian stock markets would plummet. Oil prices would rise by $10-20 per barrel. The semiconductor supply chain (Taiwan TSMC's shipping routes) would also be affected. However, a full-scale war is likely to be avoided due to the prohibitive costs for both sides, with the conflict remaining limited. Rather, the biggest risk in this scenario is the formation of a "new normal" after the clash. Once a conflict occurs, the expansion of military presence becomes further justified, and the spiral of conflict enters a new phase.
Implications for Investment/Action: U.S.-China military hotline outage/delay, changes in China Coast Guard rules of engagement (expanded application of the 2021 Coast Guard Law), intensity of physical obstruction to Philippine resupply activities at Second Thomas Shoal, deployment of new weapons (e.g., HQ-9B) to artificial islands, increase in cyberattacks
Key Triggers to Watch
- Next resupply mission to Second Thomas Shoal, Philippines — Watch whether the China Coast Guard's level of interference escalates from "water cannons" to "physical blocking/collision": March-April 2026 (monthly resupply mission)
- Progress of South China Sea Code of Conduct (COC) negotiations at the ASEAN Foreign Ministers' Meeting — Focus on legal enforceability: July 2026 (ASEAN Foreign Ministers' Meeting)
- Trends in military capability development towards the 100th anniversary of the founding of the People's Liberation Army — Linkage with Xi Jinping's "2027 Taiwan unification preparation" target: Throughout 2026-2027
- Feasibility of a U.S. President-Xi Jinping summit — Whether the South China Sea is on the agenda, and if there is an agreement on de-escalation: April-September 2026 (margins of G7/G20 summits)
- Completion of deployment of new Type 12 (Kai) anti-ship missile units to Japan's Nansei Islands — Whether China views this as "crossing a red line": Within FY2026 (by March 2027)
🔄 Tracking Loop
Next Trigger: Next resupply mission to Second Thomas Shoal, Philippines (March-April 2026) — Whether the China Coast Guard's level of interference escalates from "water cannons" to "physical obstruction" will determine the next stage of the spiral.
Continuation of this Pattern: Tracking: South China Sea U.S.-China Conflict Spiral — Next milestones are COC negotiation progress at the July 2026 ASEAN Foreign Ministers' Meeting, and linkage with China's military modernization goals towards 2027.
🎯 Oracle Declaration
Prediction Question: Will a military clash between the U.S. and China (an incident involving physical contact between vessels, aircraft collision, or use of force beyond warning shots) occur in the South China Sea by December 31, 2026?
Judgment Deadline: 2026-12-31 | Judgment Criteria: YES if an incident involving physical contact between vessels, aircraft collision, or use of force beyond warning shots occurs between the U.S. military and the Chinese military (including Navy, Air Force, and Coast Guard) in the South China Sea by December 31, 2026, and is confirmed by a reliable news organization (Reuters, AP, AFP, or official statements from national defense ministries). Water cannon or laser illumination by the China Coast Guard against Philippine vessels will be judged NO as it is not a direct U.S.-China clash.
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