In late April of 2025, Chinese coast guard personnel raised the Chinese flag on Sandy Cay in the South China Sea to assert sovereignty. This action coincided with the United States and the Philippines holding large-scale joint military exercises, escalating tensions in the South China Sea region and drawing warnings from Washington and Manila.
The footage of Chinese coast guard personnel raising the flag on Sandy Cay was broadcast on China Central Television on Friday, April 25th, stating that it was to “implement maritime control and exercise sovereignty jurisdiction.” This marked the first time in many years that China has made a high-profile assertion of sovereignty over an uninhabited reef in the South China Sea, signaling a further escalation of its expansion actions in the region.
Sandy Cay is a small sandbar located about 1.5 nautical miles northwest of Thitu Island, which is controlled by the Philippines in the Spratly Islands. The geography of Sandy Cay is highly sensitive and strategically important. According to international maritime law, if the reef remains above water surface for an extended period, its surrounding waters could claim a 12-nautical-mile territorial sea.
Thitu Island is one of the largest islands controlled by the Philippines in the Spratly Islands, with a military presence since the 1970s and basic infrastructure such as a makeshift airstrip, a pier, and essential civilian facilities. Manila is currently upgrading the runway and other infrastructure on the island to enhance defense and support capabilities.
However, due to the proximity of Sandy Cay to Thitu Island, a reinforced Chinese presence on Sandy Cay would pose a direct and serious threat to the security of Thitu Island for the Philippines.
At the same time, the United States and the Philippines are conducting the largest-ever “Balikatan” joint military exercises in the vicinity of the South China Sea. The exercise, running from April 21 to May 9, lasting three weeks, involves around 11,000 U.S. troops and 5,000 Philippine soldiers, with military personnel from Australia, Japan, and France participating as observers and in some joint operational activities.
The exercises cover island defense, island seizure operations, joint maritime and aerial warfare, missile interception, and maritime blockade, showcasing highly integrated joint operational capabilities. The U.S. has deployed the HIMARS (High Mobility Artillery Rocket System) and F-22 stealth fighter planes, emphasizing operational advantages in rapid response and long-range strike capabilities.
While Washington and Manila claim that the military exercises are “not directed at any specific country,” it is widely believed that this move is a clear response to China’s increasingly frequent military activities and land reclamation efforts in the South China Sea.
In response to China’s seizing of Sandy Cay, the U.S. National Security Council spokesman, James Hewitt, expressed “deep concern,” stating that China’s actions undermine regional stability and the principle of freedom of navigation. He emphasized that the U.S. would maintain close coordination with its allies to uphold freedom and an open order in the Indo-Pacific region.
The government of Philippine President Ferdinand Marcos Jr. condemned China’s actions, reiterating its position of “firmly defending national sovereignty and territorial integrity.” Manila also revealed its concerns that despite the temporary withdrawal of Chinese coast guard ships after the Sandy Cay incident, China may continue to escalate pressure through harassment activities.
Currently, both China and the Philippines have not engaged in direct armed conflicts over the Sandy Cay incident. However, given the escalating tensions in the South China Sea sovereignty dispute and the coverage of the South China Sea region under the U.S.-Philippines Mutual Defense Treaty, the risk of minor conflicts remains, which could impact regional security.
China’s actions at Sandy Cay demonstrate a new adjustment in its strategy to advance its sovereignty claims in the South China Sea, posing challenges to the increasingly strengthened military cooperation between the U.S. and the Philippines. The developments in the South China Sea remain a vital issue of international concern.
(This article references related reports from the Financial Times and Reuters)