The United States became a world power and acquired overseas holdings as a result of the Spanish-American War. Hawai‘i’s strategic location made it critical to the military interests of the United States. (Ireland)
The initial studies for the defense of O‘ahu’s south shore called for seacoast batteries westward along the shoreline from Diamond Head to a point immediately west of the Pearl Harbor Channel.
As early as 1901 consideration was given to placing seacoast guns in the vicinity of Waikiki, where two 10-inch guns on barbette carriages were proposed to supplement the fire of the gun and mortar batteries at Diamond Head as well as those projected for the entrance to Pearl Harbor, thus protecting both Pearl and Honolulu Harbors. (Gaines)
In 1913, Oahu had eight coastal batteries guarding the naval base at Pearl Harbor and the port of Honolulu, including four at Ft. Kamehameha; one at Ft. Armstrong; two at Ft. DeRussy and one at Ft. Ruger. The Navy had dredged the harbor and placed the dredge material at Ft. Kamehameha to build up the submerged land. (Army Corps 100 Years in Hawaii)
The early 1920s saw major changes in the US Army in Hawaii. The Hawaiian Division was formed of infantry and artillery brigades at Schofield Barracks in 1921.
The Artillery District of Honolulu was redesignated the Hawaiian Coast Artillery District on April 5, 1921, moving its headquarters from Fort Ruger to the Alexander Young Hotel in downtown Honolulu until facilities at Fort Shafter were available on June 21, 1921. (Gaines)
Between the two world wars, nearly a dozen more coast artillery reservations for seacoast batteries, searchlights, fire control stations, and command posts were established on tracts of land of various sizes and placed under the Honolulu Harbor defenses.
Prior to World War II, only the slightest defenses were provided for Oahu’s Windward Coast and North Shore. Shortly before World War II, the Harbor Defense Honolulu was also directed to oversee the initial defense of a new naval air station on Oahu’s
Windward Coast, at Kaneohe Bay. (The Harbor Defenses of Kaneohe Bay was constituted as a separate command in the latter part of 1941.)
During World War II, more gun batteries and fire control installations were built throughout the Honolulu harbor defenses.
During much of this same time, “Hawaii has started in the footsteps of America by projecting a railroad around the island of Oahu, and actually perfecting, within the period from April 1st, 1889, to January 1st, 1890, a well equipped railroad in running order, extending from Honolulu along the southern shore of the island to a temporary terminus at Ewa Court House, a distance of twelve miles.”
“A hundred men told him his scheme was infeasible where one offered encouragement. He believed he was right, and so put forth every endeavor to secure a franchise, which was granted to him only after vigorous legislative opposition to the measure.”
“With all the disadvantages that remoteness from the manufacturing centers of America offered, Mr. Dillingham undertook the contract of building and equipping the railroad. Rails were ordered in Germany, locomotives and cars in America, and ties in the home market; rights of way were amicably secured, surveyors defined the line of road, and grading commenced.”
“The work was prosecuted with the utmost speed consistent with stability and safety, and there was hardly a day’s delay from the time grading commenced, in the spring of 1889, till September 4th following, when the first steam passenger train, loaded with excursionists, left the Honolulu terminus, and covered a distance of half a mile.” (Whitney)
The OR&L railroad had built a spur from the coast to Wahiawa in 1905, to haul cane and pineapples down to the coast and later to haul men and supplies from Pearl Harbor to Schofield Barracks in Wahiawa through Waikakalaua Gulch in Waikele.
Right after the attack on Pearl Harbor the Army commandeered their entire stock of rails and bridge timbers.
A cut-off between Wahiawa and the windward side of the island was vital to defense, the brass decided it had some 90-ton railway guns for coast defense and feared that enemy attack might sever the main line and make it impossible to spot them along the shoreline in case the Japanese tried to make a landing.
The cut-off was be a sort of a secret back-door short cut. And so, an extremely hush-hush track was laid down from Wahiawa to Haleiwa.
The OR&L only had two miles of steel in stock, and the cut-off was pieced out with light plantation rail. This “secret railroad” provided a short cut from Pearl Harbor to Army facilities at Kahuku on the north shore of O‘ahu and then over to the windward side.
Fortunately, it was never needed; and, the chances of the heavy guns ever negotiating it successfully were slim, to say the least. (Kneiss)
With the end of World War II came the realization that many of the various batteries and coastal defense guns were no longer capable of meeting the needs of the US military in Hawaiʻi. The giant guns were cut up and sold for scrap, having never fired a shot in anger or defense.