The South China Sea is a region of overlapping territorial claims, primarily between China and several Southeast Asian states. China asserts a “nine-dash line” claim, covering vast areas also claimed by the Philippines, Vietnam, Malaysia, and Brunei. International law does not recognize China’s expansive claim, and a 2016 international arbitration tribunal ruled in the Philippines’ favor.
Since 2023, tensions between China and the Philippines have sharply escalated. Chinese coast guard and maritime militia vessels have used water cannons, laser devices, and ramming tactics to obstruct Filipino resupply missions to contested maritime features such as Second Thomas Shoal. The Philippines has strengthened defense ties with the U.S., Japan, and Australia and is considering expanded joint patrols, which are moves China condemns as foreign interference.
ASEAN does not maintain a unified security force, and joint patrols historically involve only limited regional participation.