The South China Sea: America's Next Military Crisis?

What Is at Stake

The South China Sea carries approximately $3 trillion in global trade annually — including massive shares of energy imports for Japan, South Korea, and Taiwan. China claims sovereignty over roughly 90% of this body of water through its "Nine-Dash Line," a claim that was ruled illegal under international maritime law by an arbitration tribunal in 2016.

China has ignored that ruling. It has instead proceeded to build artificial islands on reefs and shoals throughout the sea, construct military-grade airstrips and missile batteries on those islands, and increasingly confront other nations' ships and aircraft that transit what international law considers open ocean.

The Islands Are Military Assets

What China has built in the South China Sea is not ambiguous. The Spratly Islands constructions include:

• Reinforced concrete runways capable of landing military aircraft, including bombers
• Missile defense systems including HQ-9 surface-to-air batteries
• Anti-ship missile batteries
• Radar and signals intelligence facilities
• Hangars and port facilities for naval vessels

In a conflict scenario, these installations would allow China to project military power across a vast area, complicate US naval freedom of movement, and potentially threaten Taiwan and allied shipping simultaneously.

The Claimant Countries

China's claims overlap with those of Vietnam, Philippines, Malaysia, Brunei, and Taiwan — all of which have legitimate historical fishing rights and exclusive economic zone claims in portions of the sea. China has used water cannons, laser systems, and direct confrontation of Philippine Coast Guard vessels conducting routine resupply missions to its own territory.

The Philippines, a US treaty ally, has increasingly pushed back — particularly under President Ferdinand Marcos Jr. — and has asked the US to clarify whether the Mutual Defense Treaty covers Philippine ships in the South China Sea. The answer matters enormously.

The US Freedom of Navigation Operations

The US Navy regularly conducts "Freedom of Navigation Operations" — sending warships through waters that China claims but that international law says are open ocean. These are important signals, but they do not change the physical reality on the water.

China interprets these operations as provocations. The US argues they are legally required to maintain the principle that international waterways remain open. Both are true, and neither changes the trend line.

The Trump Complication

The Trump administration's approach to China is simultaneously more hawkish on trade and less coherent on security. Reducing alliances with the very countries — Philippines, Japan, South Korea — that would need to coordinate any response to Chinese aggression undermines the deterrence these countries represent.

A Trump-era grand bargain with China on trade that implicitly reduces pressure on Chinese territorial behavior in the South China Sea would be catastrophic for regional security.

FAQ

Does the US have treaty obligations in the South China Sea? The US Mutual Defense Treaty with the Philippines covers attacks on Philippine "armed forces, public vessels, or aircraft" — language that almost certainly covers Coast Guard vessels. The US has stated that the treaty does apply to the South China Sea, but the specifics of what triggers it remain contested.

Can China legally claim the South China Sea? No. The Permanent Court of Arbitration ruled in 2016 that China's Nine-Dash Line claims have no basis in international law. China rejected the ruling.

Is a military conflict in the South China Sea likely? Most analysts consider a large-scale military confrontation unlikely in the near term, but low-level incidents — ship confrontations, aircraft intercepts — are increasingly common and raise the risk of accidental escalation.