A key goal in the Pacific was to hold Oʻahu Island as a main outlying naval base and to protect shipping in the waters around the Hawaiian Islands. The War Department looked to much larger reinforcement of Hawaiʻi. This led to plans for garrisoning the other islands of the Hawaiian group. And, Hilo was a natural choice.
In 1908, construction began on the Hilo Bay breakwater along the shallow reef; piers were built and extended by 1927. A mobile field battery of 155-mm guns was set up in December 1941. Four 4-inch naval guns were later emplaced in 1942. The Hilo battery was abandoned in 1945. The exact locations are undetermined.