Recall the year 1910. Battery Harlow stands as a testament to early 20th-century military engineering. It was a crucial part of Fort Ruger’s defense system.
Battery Harlow is one of the many batteries of Fort Ruger. Fort Ruger started its construction in April 1907 with Battery Harlow. Construction concluded by March 1910. It is a massive structure built with reinforced concrete. It is embedded behind Diamond Head Mountain’s outer slopes.
Three large bunkers formed the core of Battery Harlow. These bunkers were separated by courtyards. These courtyards functioned as platforms. Eight 12-inch mortars were stored in these courtyards. These mortars were designed to protect O’ahu from enemy attacks. Specifically they defended against the Imperial Japanese Navy. The mortars could fire up to eight miles. They could reach both Honolulu and Pearl Harbor.
Battery Harlow had a 360-degree field of fire. Its design allowed it to fire over Diamond Head Crater out to sea. The battery could even hit Kaneohe Bay. That is located over the mountains to the north.
Imagine the structure. It is shaped like a capital E. The arms of the E house two pairs of four-mortar gun pits. The building itself has thick concrete walls. It is covered with feet of soil. Inside were fire control facilities and offices. There were storerooms for powder and shells. An underground power room kept the battery running. A 25kW generator powered by a 50 HP gasoline engine provided electricity. Lantern alcoves provided light during power failures.
The central part of the E contained a mechanical communication system. This system relayed firing information to the gun crews. Concrete megaphones were built into the wall. Fire control officers used mechanically cranked numbers. These numbers signaled elevation and azimuth settings to the gun crews.
Battery Harlow operated from 1910 to 1943. The US Army retired it in 1943. The artillery was dismantled in 1950.
Interestingly Battery Harlow has served as a backdrop. It was used for scenes in movies and television shows.
As of December 2018 there were plans to open Battery Harlow. It would become a pedestrian entrance to Diamond Head Mountain. Currently the Hawaii National Guard uses Battery Harlow for storage. Public access is restricted. The hiking trail remains closed.
Battery Harlow stands at Diamond Head Road & Makapuu Road. It remains a silent witness to a bygone era. It is a reminder of O’ahu’s strategic importance. It is a symbol of early 20th-century military might.