Why the U.S. Must Strengthen Its Commitment to Protect Allies in the South China Sea Against Chinese Aggression

By Jeremiah Monk

Introduction

The South China Sea remains one of the world’s most critical regions for international shipping, trade, and geopolitical balance. Yet, Chinese Coast Guard aggression toward allied nations has escalated, straining the stability of the region and testing the commitments of the United States to protect its allies. Although the actions taken by Chinese forces often fall below the threshold of armed conflict, they constitute a persistent, calculated form of aggression aimed at expanding Chinese influence and undermining allied resolve. This aggression poses a direct threat to the security interests of U.S. allies and partners, such as the Philippines, Vietnam, and other Southeast Asian nations. It is essential that the United States adopt a more proactive stance to protect these allies effectively, as the current U.S. posture has shown insufficient deterrent power. This article explores why the U.S. has a responsibility to intervene, provides recent examples of Chinese Coast Guard actions, and proposes three innovative measures to better deter aggression and safeguard allied interests.

The U.S. Responsibility to Protect Allied Nations in the South China Sea

The United States has long maintained strategic alliances in the Asia-Pacific region. Alliances with nations like the Philippines and Japan have been instrumental in establishing a balance of power and promoting peace and security. The South China Sea is vital not only for its resources and economic significance but also as a symbol of regional freedom against coercion. When the U.S. extends its protection and strengthens its commitments, it reinforces the security structure that prevents any one nation from dominating the region.

However, Chinese actions have challenged this structure. China’s Coast Guard, operating under a strategy of “grey zone” tactics, pursues aggressive actions that fall below the threshold of military conflict, making it difficult for allied nations to justify self-defense responses. This aggression includes ramming, water-cannoning, and maneuvering dangerously close to vessels of allied nations. Despite these provocations, the U.S. response has largely been passive, relying on diplomatic statements and freedom-of-navigation operations, which have so far proven inadequate in deterring China’s actions.

Recent Examples of Chinese Coast Guard Aggression

Over the past few years, Chinese Coast Guard actions have repeatedly infringed on the sovereignty of neighboring countries and raised tensions in the South China Sea. In July 2023, for example, Chinese vessels reportedly rammed Philippine fishing boats near the Spratly Islands, causing damage to the boats and endangering the lives of Filipino fishermen. This incident was not an isolated one. A similar event occurred earlier in 2023, where a Chinese vessel blocked a Philippine supply boat in the Second Thomas Shoal, obstructing it from resupplying a military outpost. Such actions are designed to intimidate and coerce while avoiding a direct confrontation that might provoke an armed U.S. response under its mutual defense treaty with the Philippines.

Moreover, China has established a formidable presence with its “maritime militia,” an armed group of fishing vessels that supplement the Chinese Coast Guard’s patrols. These militia vessels often crowd around disputed territories and have been reported encircling islands occupied by other nations, preventing these countries from conducting routine patrols or fishing activities in their own waters. In many cases, these actions are coupled with warnings from the Chinese Coast Guard, claiming these territories as Chinese waters and forbidding other nations’ vessels from approaching.

The Failure of the Current U.S. Posture in Deterring Aggression

While the U.S. has taken steps to counter China’s assertiveness, including increasing freedom-of-navigation operations and conducting joint military exercises with allies, these measures have done little to deter Chinese Coast Guard aggression. Freedom-of-navigation operations serve as symbolic affirmations of open seas but fall short of challenging China’s day-to-day harassment of U.S. allies in the region. Similarly, joint exercises may improve allied preparedness but do not directly address the immediate needs of smaller nations facing Chinese coercion.

Without a more proactive approach, the U.S. risks signaling to its allies that it is unwilling or unable to defend their interests against Chinese aggression. This lack of action could embolden China to continue, or even escalate, its coercive tactics. To demonstrate its commitment to its allies, the U.S. must explore innovative strategies that directly respond to the unique challenges posed by Chinese Coast Guard actions.

Proposed Measures to Deter Chinese Coast Guard Aggression

The United States needs creative, assertive measures to counter Chinese aggression in the South China Sea effectively. The following three options offer a proactive approach to better deter the Chinese Coast Guard while enhancing protection for allied nations.

1. Deployment of Combined Submersible Drone and Propeller-Entanglement Device Systems

To effectively patrol and defend strategic areas in the South China Sea, the U.S. could help allies deploy defensive propeller-entanglement devices in key areas. The devices, which can be as simple as a tangle or rope or an advanced high-tensile net, could be deployed by fishing vessels or by submersible drones. Ropes can ensnare and seize Chinese propellers, rendering aggressive vessels unmaneuverable.  Drones, which are designed to be stealthy and maneuverable, could be stationed at key choke points or near allied waters to monitor and, if necessary, temporarily disable hostile vessels. By deploying underwater drones to patrol contested waters, the U.S. could create a persistent surveillance presence, enabling real-time monitoring and, if Chinese vessels engage in aggressive maneuvers, immediate defensive action.

Equipped with propeller-entanglement systems, these drones could discreetly release entangling lines or nets to immobilize hostile vessels if they approach too closely to allied ships. This non-violent, defensive measure would complicate China’s use of close-contact intimidation tactics and create real consequences for any harassment of U.S. allies’ vessels. By combining surveillance and deterrence in one system, the U.S. could enhance regional security while avoiding direct military confrontation.

2. Use of High-Intensity Light or Laser Deterrents

Deploying non-lethal high-intensity lights or low-energy lasers on U.S. or allied vessels could deter Chinese ships that engage in close-harassment tactics. These tools could disorient or temporarily impair the vision of operators on aggressive vessels without causing permanent harm, making it difficult for them to engage in close-contact intimidation of allied ships. High-intensity lights or lasers could also be deployed on automated floating buoys near contested zones, creating a low-cost deterrent barrier that makes it uncomfortable and risky for Chinese vessels to continue their incursions.

Using high-intensity lights and lasers would allow smaller allied vessels to maintain a safe distance from intimidating Chinese ships, giving allied nations a form of deterrence that is reversible, humane, and legally compliant. This approach also aligns with current technological trends in non-lethal deterrence, providing a relatively low-risk means of pushing back against grey-zone tactics without engaging in open conflict.

3. Crowdsourcing Surveillance with Private Fishing Fleets and Public "Naming and Shaming"

To increase surveillance capabilities and exert diplomatic pressure, the U.S. could assist allied nations in outfitting local fishing fleets with GPS tracking, audio, and video-recording devices, creating a “civilian surveillance network.” These fishing fleets, with their daily presence in contested waters, could capture real-time evidence of Chinese Coast Guard harassment and other aggressive actions. This network would serve as a passive deterrent by vastly increasing the visibility of China’s activities in the region.

Beyond simply gathering data, this information could be publicly released in a “naming and shaming” campaign to spotlight and expose each instance of Chinese coercion. High-quality video evidence and GPS data, shared on international platforms, would show the provocations and intimidation that China uses against smaller nations in the South China Sea. Such exposure would create diplomatic consequences, drawing negative attention to China’s actions from global audiences, international media, and human rights organizations. By documenting and broadcasting these incidents, the U.S. and its allies could weaken China’s standing and raise global awareness, making it harder for China to sustain its aggression in the court of public opinion.

4. Employment of Quick-Expanding Foam Spray as a Non-Lethal Deterrent

A quick-expanding foam spray could be deployed as a non-lethal tool to temporarily disable hostile Chinese Coast Guard or militia vessels engaging in aggressive maneuvers. This type of foam, which rapidly expands and hardens on contact, could be deployed by allied or U.S. vessels to obstruct essential parts of a threatening vessel, such as its propellers or water intake valves. The foam acts as an immobilizing agent, effectively preventing the vessel from maneuvering without causing permanent damage.

This method of deterrence provides a powerful psychological and physical barrier by halting aggressive vessels in their tracks. The quick-expanding foam can be deployed through specialized canisters or launchers, requiring minimal setup. Additionally, this foam is biodegradable and non-toxic, ensuring minimal environmental impact while providing a reversible but highly visible deterrent. Using this method, allied nations and U.S. forces could respond to encroaching vessels in a measured yet assertive manner, creating an effective line of defense without escalating to direct military confrontation.

Conclusion: A New U.S. Strategy for a Stable South China Sea

The United States faces a pivotal moment in its commitment to the security and sovereignty of its allies in the South China Sea. Chinese Coast Guard aggression has grown more audacious, testing the limits of international tolerance and the efficacy of the U.S. response. As current U.S. strategies have done little to curb this behavior, it is imperative for the U.S. to adopt a more robust, proactive approach that addresses the specific nature of Chinese aggression in the region.

The proposed measures—submersible drones, propeller-entanglement devices, high-intensity light or laser deterrents, civilian surveillance networks, and expandable foam—are examples of viable, innovative solutions that can be employed to defend US allies and enhance maritime deterrence without escalating to full-scale military conflict. These actions could strengthen allied nations’ defenses, demonstrate U.S. commitment, and create tangible consequences for China’s coercive tactics.

In implementing these strategies, the U.S. can reaffirm its role as a defender of freedom and stability in the Asia-Pacific region, ensuring that its allies do not stand alone against the challenge of Chinese aggression. By moving beyond symbolic gestures and adopting a stance that actively addresses China’s grey-zone strategies, the U.S. can effectively protect the South China Sea’s freedom and its allies’ sovereignty, sending a resounding message to all nations that aggression, in any form, will not go unchecked.