Second Thomas Shoal: The Next South China Sea Flashpoint?

Daniel Judd, May 15, 2024

In 1999, the Philippines Navy intentionally grounded one of their navy ships, the BRP Sierra Madre onto a small shoal, known as the Second Thomas Shoal in the South China Sea out of frustrations regarding territorial disputes with the People’s Republic of China (PRC). Just four years earlier, in 1995, the PRC took control of Mischief Reef, a neighboring geographical feature within the same island chain of the Spratly Islands [1]. In the past few decades, the Spratly Islands have been the focal point for general unrest in the region as the PRC aggressively extends its sphere of influence into the South China Sea. China has argued that the majority of the South China Sea territory belongs to China using the historical claim of the nine-dash line to legitimize their claims. These claims, however, have not been acknowledged by most other countries and violate internationally agreed upon and UN-ratified ocean Exclusive Economic Zones (EEZ) for a multitude of South Asian nations, notably Vietnam, the Philippines, Malaysia, and Indonesia [2]. As tensions begin to rise, it becomes increasingly possible that a military escalation will occur in the region, likely as an accidental altercation within the Spratly Islands chain. Even if unintentional, such an altercation could have significant and widespread repercussions for the nations involved as well as the South China Sea region depending on national alliances and US intervention. 


The South China Sea is a region of significant importance for both China and many other neighboring Southeast Asian nations as it serves as a political, economic, and strategic lynchpin within the region. The South China Sea holds substantial economic value with its sea shipping lanes that facilitate around 30% of the world’s annual trade tonnage. The sea itself also possesses valuable natural resources such as fossil fuels, natural gas, fisheries, hydrocarbons, and combustible ice [3]. In addition to impressive economic resources, the island chains in the South China Sea play an integral role in strategic control of the sea and the regions surrounding it. Having control of these island chains allows a state to have greater influence over most other parts of Asia in the economic and political spheres. Beyond the obvious commercial and military benefits of controlling the sea routes in the region, the South China Sea also provides China with a buffer from the US in case of a war or conflict involving regions like Taiwan. By gaining control of this region, China would have the means to monitor and prevent US naval vessels from entering into unwanted areas of the South China Sea [4]. 


To gain a further understanding of the current flashpoint in the Spratly Islands, it is important to go over the history of Chinese expansion throughout the region. China has historically claimed much of the South China Sea, with the current Chinese Communist Party (CCP) regime claiming historical control of the region since over 4,000 years ago during the Xia Dynasty [5].  The region's control was shown through a U-shaped Nine-Dash Line depicting a large swath of the South China Sea as under China’s direct control. However, much of this area currently falls into the EEZ of nations such as Vietnam and the Philippines, which has contributed to the disputes happening now. China’s behavior in the region over the past 60 years appears to follow a recurrent trend of assertiveness with periods of intermittent escalations and de-escalations. 


In 1950, China made its first move into the region by taking Woody Island, an island in the north of the sea that had been disputed with Vietnam. Following this escalation, China delayed further expansion by several decades, until it took over Fiery Cross Reef and Johnson Reef in the late 1980s. This expansion was once again met with strong disapproval from Vietnam. This time, China’s expansionism resulted in an armed skirmish which led to the death of over 50 Vietnamese soldiers according to Vietnam state reports [6]. Once again, China entered into a period of relative peace in the region until its sudden capture and development of the Mischief Reefs in 1994. This development was met with pushback and a statement of strong disapproval by the Philippine government, leading to several large protests in Manila against the PRC [7]. Following the extension of influence to Mischief Reefs, China entered a period of delay once more, having minimal expansion in the region until 2012. In 2012, China took over and began development in the Scarborough Shoal, a region within the Philippines’ EEZ. In response, the Philippine government filed an international case against China in the International Court of Arbitration in Hague. The International Court ruled against China as it deemed the nine-dash line illegitimate and condemned China’s recent expansion. China has ignored this ruling — denouncing it to be “null and void” — and continued its expansion in the region [8]. Since 2012, the PRC has spent lots of resources modernizing military bases and creating artificial islands on many of these shoals and atolls. For instance, China has installed advanced radars, anti-ship and anti-aircraft missiles, and a multitude of other military equipment throughout the region [9]. Following 2020, tensions have begun to rise again over the Second Thomas Shoal, another small feature in the Philippines EEZ, threatening peace and stability within the region. 


China and the Philippines have had disputes over the Second Thomas Shoal since the 1990s when Beijing first began aggressively expanding its control over the South China Sea. This expansion led to the grounding of the Sierra Madre in 1999. Since then, the ship has acted as a makeshift garrison and outpost allowing the Philippine Navy to enforce its claim on the shoal and the surrounding island chain [10]. In recent years, China has become increasingly more aggressive towards Philippine supply ships coming to resupply the soldiers based in the Sierra Madre. In 2021, Chinese Coast Guard vessels engaged in a makeshift blockade around the shoal preventing Philippine supply ships from reaching their garrison. Chinese ships have also been reported to have fired water cannons and military-grade blinding lasers at Philippine ships, along with repeatedly ramming into them with their own vessels [11]. These developments led the Philippines' former Secretary of Foreign Affairs Teodoro Locsin to tweet: “China, my friend, how politely can I put it, Let me see… O…GET THE F--- OUT,” [12]. Although Locsin later withdrew the remark, this indicated a major negative shift in Philippine foreign affairs towards China under Duterte, a historically pro-China leader. As tensions have continued to escalate with China a new, more pro-US president Bongbong Marcos has begun to align the Philippines closer to the US, doubling down on the Enhanced Defense Cooperation Agreement (EDCA) [13]. The EDCA bolstered the pre-existing mutual defense alliance between the two nations that has been around since the 1950s. As part of this agreement, the two nations have agreed to create four new shared military bases in the Philippines, making it easier for the US to assist in conflicts in the Indo-Pacific [14]. Although there have been no times when the US has had to step in in defense of the Philippines thus far, tensions in the region continue to grow. History in the region, such as the skirmish at Johnson Reef, has shown that continuous scuffles between the Philippines and China’s coast guards can easily result in a localized skirmish involving gunfire and potential casualties. Such localized events, even if accidental, can escalate to have much more worrying consequences if not addressed properly.  


A potential military altercation in the Second Thomas Shoal could have extra unintended consequences due to the recently reinforced EDCA. Since the US and the Philippines have an official mutual defense treaty, the US would be obligated to help defend its ally if the Philippines were involved in any form of military conflict with China. If the conflict escalates and the US officially gets involved with its military, then it may quickly spread in size and scope to become a large regional — if not global war — between the US and China. The chances for such rampant escalation are currently low as both countries are unlikely to want a full-scale war with one another [15]. 


The US has released several contingency plans in response to Chinese militarization on the Scarborough Shoals, and for deterring a potential conflict between China and the Philippines. According to these plans, the US would publicly condemn China for any actions against the Philippines, enact trade restrictions on China, and supply its Philippine ally with arms, resources, and military training [17]. The US has strong interests in keeping China from gaining complete control of the region as China has been establishing a network of strategic, economic, and military ports spanning from East Africa to the South China Sea. This chain of ports, along with the shipping lanes accompanying them is known as the String of Pearls [18].  With unrestricted access to the South China Sea, China would be able to gain a significant economic advantage, much to the detriment of the US. Such actions by the US could further destabilize an already unstable region, even without a full-scale war, by causing Beijing to ramp up its militarization of the region and further fray relations between the two global powers. 


No matter the outcome, China’s rapid spread and extension of its sphere of influence throughout the South China Sea Region is a cause for attention for policymakers throughout the globe because it demonstrates that the PRC is becoming increasingly emboldened to challenge the current world order and shift the current global power balance into its own hegemonic favor. As China extends its military prowess into the South China Sea, it can begin to turn its attention towards its main goal in the region, that of reunifying with Taiwan. With the increased resources and power gained from controlling the South China Sea, China will likely have a higher probability of being successful in achieving its cardinal goal. A conflict over Taiwan, which the US may be involved in, could end up being the largest war in the Pacific since World War II. As China continues to ignore international condemnations of incursions into other nation’s EEZ, it becomes more likely that the US or another power will become involved. It is imperative to continue closely monitoring the situation in the South China Sea, not only to ensure the sovereignty of Southeast Asian nations but also for the US to ensure stability within the current power balance with a rising hegemonic challenger: China.


[1] “What’s behind Rising China-Philippines Tensions in the South China Sea?” Al Jazeera, August 9th, 2023.

[2] Mensah, T., The South China Sea Arbitration.

[3] CRS, Congressional Research Service. “China Primer: South China Sea Disputes.” US Congress, August 21st, 2023.

[4] CRS, “China Primer: South China Sea Disputes.”

[5] Al Jazeera, “What’s behind Rising China-Philippines Tensions in the South China Sea?”

[6] Viet, Quoc. “‘vòng Tròn Bất Tử’ Trên Bãi Gạc Ma (‘Immortal Circle’ on Gac Ma Beach).” TUOI TRE ONLINE,, August 25th, 2017.

[7] McCarthy, Terry. “Reef Wars.” Timeasia.Com, TIME, March 8th, 1999.

[8] Santos, Matikas. “China’s ‘nine-Dash Line, Historic Rights’ Invalid – Tribunal.” INQUIRER.Net, July 13th, 2016.

[9] Pitlo, Lucio Blanco. “The Second Thomas Shoal Incident and the Reset in Philippine-U.S. Ties.” Asia Maritime Transparency Initiative, December 17th, 2021.

[10] Elemia, Camille. “What It Feels like to Be the Target of China’s Water Cannons.” The New York Times, December 11th, 2023.

[11] CRS, “China Primer: South China Sea Disputes.”

[12] @teddyboylocsin. “China, my friend, how politely can I put it, Let me see… O…GET THE F--- OUT,” Twitter, May 2nd, 2021.

[13] Elemia, Camille. “What It Feels like to Be the Target of China’s Water Cannons.”

[14] Chang, Felix. “Hot and Cold: The Philippines’ Relations with China (and the United States).” Foreign Policy Research Institute, December 8th, 2021.

[15] Vergun, David. “New EDCA Sites Named in the Philippines.” U.S. Department of Defense, April 3rd, 2023.

[16] Chang, Felix. “Hot and Cold: The Philippines’ Relations with China.”

[17] Mastro, Oriana. “Military Confrontation in the South China Sea.” Council on Foreign Relations, May 21st, 2020.

[18] Ellis, Chris. “China’s String of Pearls Strategy.” China Briefing News, January 9th, 2013.