Linking the Two Seas: Japan-Philippines Defense Ties and the East China Sea-South China Sea Nexus
January 30, 2026
Months after the Japan-Philippines Reciprocal Access Agreement (RAA) entered into force on September 11, 2025, Tokyo and Manila signed a new logistical agreement on January 15, 2026. The Acquisition and Cross-Servicing Agreement (ACSA) sets forth a bilateral framework for reciprocal provision of supplies and services between the Japanese Self-Defense Forces (SDF) and the Armed Forces of the Philippines (AFP).
Tokyo has also been funding and delivering maritime security instruments including coastal radar systems and rigid-hulled inflatable boats (RHIBs) for the Philippine Navy through the Japanese Official Security Assistance (OSA) channel. In mid-January 2026, as the two sides finalized the ACSA, Japan also added an OSA-backed infrastructure package including boathouses and slipways to house and operate the RHIBs in parallel.
The implications of these arrangements go far beyond the Japan-Philippines bilateral relationship. The rapidly expanding defense cooperation between the two, situated on the opposite ends of the First Island Chain, is unfolding amid the ongoing maritime disputes and heightened diplomatic friction with China. Japan-Philippines defense cooperation points to a quiet, but consequential strategic shift in East Asian security dynamics: China's two critical maritime security fronts — East China Sea and South China Sea — are now being stitched together into one, connected theater.
Author: Mengzhen Liu, Assistant Research Fellow at Huayang Center for Maritime Cooperation and Ocean Governance.
This article was originally published on The Diplomat, titled "China's Emerging Two Front Problem". Read the complete article at: https://thediplomat.com/2026/01/chinas-emerging-two-front-problem/
