A Chinese warship was photographed monitoring U.S. and Philippine naval forces on Monday during a joint exercise in the fiercely contested waters of the South China Sea. The event marked the first Maritime Cooperative Activity (MCA) of 2026 between the U.S. and the Philippines , as the Mutual Defense Treaty allies continue to strengthen defense ties—including through multilateral exercises and the U.S. deployment of mid-range missiles to the Southeast Asian country—amid tensions with China .