a large US military base in the Philippines. Inlet of the South China Sea, southwestern Luzon, Philippines. From 1901 it was the site of the U.S.-operated Subic Bay Naval Station, the largest naval installation in the Philippines. The area suffered heavy damage in World War II and was occupied by the Japanese in 1942-44. The base played a prominent supply and maintenance role in the Vietnam War (1955-75). Control of the bay was transferred to the Philippines in 1992, and it subsequently was redeveloped as a free-trade zone and recreational and tourist destination