Before the "Pearl Harbor" attack, the U.S. army spent 40 years to protect Pearl Harbor from the Japanese attack, and developed a complete defense system on Oahu, but it did not play any role in the "Pearl Harbor" attack.
One: Why the U.S. Pacific Fleet is stationed at Pearl Harbor
The Hawaiian Islands, located 2,400 miles southwest of the continental United States, have nothing between the islands except the ocean, and the island chain itself stretches for more than 1,500 miles from northwest (Midway) to southeast (Hawaii) with 7 major islands. They are the most isolated inhabited places on Earth, with no closely connected continents and no significant islands nearby. Indigenous Polynesians have lived in the Hawaiian Islands for centuries. Europeans visited the island for the first time in 1778, and unlike other areas, the islands were not occupied or developed by colonial powers, and in the 19th century it was mainly immigrant American merchants, and in 1876 the Kingdom of Hawaii was forced to cede Pearl Harbor as a coal-loading base to the United States in exchange for the duty-free export of raw sugar to the United States. In 1893, American merchants overthrew the King of Hawaii, and in August 1898, the United States formally annexed the islands, and in 1898, the Spanish-American War broke out, and the United States acquired other Pacific territories such as Guam and the Philippines.
Since there were no other islands or ports in the eastern Pacific, and if there were no support bases in the vast Pacific Ocean, the navy requiring frequent repairs and supplies would not be able to sustain, and the Hawaiian Islands, strategically important for early sea and air transport, immediately became an important coal and logistics station, and garrisons were quickly sent from the United States to Oahu, where U.S. troops have been stationed ever since. In 1914, the completion of the Panama Canal increased hawaii's strategic importance, and Oahu soon became an important part of all potential Pacific war plans, and the Hawaiian Islands, especially Oahu, had an important strategic position for U.S. defenses in the eastern Pacific and the west coast of North America, and by establishing military bases near Hawaii, Alaska, and the Panama Canal, it was possible to maintain defensive borders thousands of miles from the population centers of the west coast, thus requiring a strong defense system.
Oahu is the third largest island in the Hawaiian Archipelago and the only island with an important natural harbor. The Pearl Harbor Lagoon is located on the southern coast of Oahu, and the port and entrance to the neighboring Port of Honolulu were initially obstructed by coral reefs and accessible only by shallow water vessels. Oahu's natural features are important for its military defenses. Two large parallel mountains protect a large valley in the center of the island, providing excellent defensive lines to prevent invading troops from entering any one of the coasts, coupled with the weather and sea conditions on the north shore, and the location of the only good harbor and population center on the south shore, the southern coast of Oahu is clearly the only defensive place, which greatly simplifies the defense plan, the volcanic rocks and rugged terrain of the island, facilitating the excavation of forts and other defensive facilities,
TWO: The construction plan of the Oahu Fortress"
By 1900, the U.S. coastal defense system was already very developed, and the 26 major ports on the continental United States were equipped with modern artillery, and most of them were equipped with mine defense systems. This new generation of fortifications is equipped with searchlights for night shooting, power plants and new fire control systems, with important garrisons, permanent barracks and other base buildings. The U.S. Army Corps of Engineers spent a lot of military activity designing and building, and the U.S. Army Ordnance Department also spent a lot of military activity to develop these weapons.
In September 1901, a local committee of U.S. Army engineers and artillery officers was formed to provide the framework for Oahu's permanent coastal defenses, including land acquisition, costs, and garrison needs. These early proposals all foresaw the dual defenses of Pearl Harbor (a coal port and a future naval base) and Honolulu (the largest commercial port). Fortunately, the two were only 7 miles apart, and the largest artillery on the coast was able to cover both locations at the same time. Honolulu benefits from natural openings offshore coral reefs that facilitate sea access. Access to Pearl Harbor is limited by the reef, but its potential as a major anchorage and naval base is recognized and could be improved by dredging. The defense plan would be to install 12-inch artillery and mortars on the east side of the pearl harbor entrance.
The same type of weapons were installed in the eastern part of Honolulu, with a small outpost on Waikiki Beach between them, fitted with 10-inch artillery. Small rapid-fire guns will complement the defense of small ships, which will be placed in each fort and in the crater of Panche Bay, located between the two ports. A controlled minefield would block narrow access to Honolulu, and the Commission also recommended the deployment of two naval coastal defense monitors on Oahu. Land defense requires only a few siege guns to cover important passes in the two mountains so that coastal defense works and ports are not captured from the rear. The garrison of this defensive system will be 4 coastal artillery companies (increased to 10 in wartime) and 2 infantry battalions. At this stage, the defense of Oahu was placed in the second category of priority, after the Philippines. Probably due to the fact that the situation at Pearl Harbor has not improved, and there is no explicit decision to develop the port as a major base.
The Commission's recommendation was soon revised by the War Department, and the newly developed 356 mm gun would be deployed on Waikiki Beach in order to bring the entrances to Pearl Harbor and Honolulu ports all under its fire control; The 16 305 mm white guns will be divided into two groups, 8 guns to fill the gaps in the defensive fire of the left and right flanks of the battery, and another 8 to be redeployed on the eastern side of Diamond Head mountain to cover the anchorage east of Oahu: two more batteries equipped with 76 mm guns will be added to strengthen the protection of the minefield: the forts originally planned for construction in Puuraua were abolished. These changes result in a decrease of $318,660 in total projected expenditures. This final proposal is close to the first phase of the Oahu Coastal Defense, which was eventually built in the following years.
Three: The first phase of the construction of the Oahu Fortress
The U.S. Congress first allocated forts off the coast of Hawaii in the Defense Act passed in June 1906, and a large appropriation from 1907 to 1912 built eight more permanent forts. Fort Kamehameha was on the east bank of the entrance to Pearl Harbor, and because of the gentle terrain, it was relatively easy to build, and the height of the gun position was somewhat low, but the firing range was very open. Originally Kamehameha Fort consisted of four coastal forts, which were distributed along the coast from east to west. Fort Armstrong, from the coastal bank of Fort Kamehameha, on the coast near the Port of Honolulu Immigration Quarantine Station, is a small coastal defense fort that serves as the main control station for the defense minefield, with only one battery, equipped with 2 m1903 type 76 mm guns, which can cover the entire minefield.
The largest and best-equipped Randolph Battery of the time was built on Fort Drusy on Waikiki Beach, with two 14-inch cannons. Mimicking the layout of a large battery, the fort is a reinforced concrete double-decker turret with an open gun position on the upper level, the gun is placed on a concealed gun mount, and a thick protective chest wall is built on the front, usually composed of cement and sandbags; The lower level is an ammunition depot, and shells and shot packs are delivered to the gun positions on the upper level by means of a built-in elevator. The turret is equipped with two m1908 m1 152 mm guns, also consisting of an open gun mount with a parapet and a tightly guarded ammunition depot. Rugerborg was selected as a mortar position in the very prominent Diamond Head Crater, with only 1 battery equipped with 8 American fortresses eliminating the surplus 305 mm white cannon, because the white artillery trajectory was curved, it could be deployed very close to the crater, very hidden, to avoid being hit by the counterattack fire of enemy ships, the main task was to suppress the enemy troops landing on the coast near the port of Honolulu, each fort was equipped with power stations, barracks, officer quarters, supply depots, hospitals and engineering facilities, And other infrastructure closely related to the operation of the fort and the lives of officers and soldiers.
These forts are equipped with fire control stations for sighting equipment, the largest fire control station is at Leahy Peak at an altitude of 230.9 meters in the southern foothills of Diamond Head Mountain, is a complex structure, a large-scale shooting command center, can provide shooting support for the surrounding multiple forts, from top to bottom divided into four floors built in the mountain, each floor is equipped with observation equipment and communication command facilities, the floors are connected by a spiral staircase, as well as a cable car for transporting supplies and small dormitories, since its completion has been the command center of Oahu, It has remained in good working order to this day. The U.S. military also equipped each fort with power stations, barracks, officer quarters, supply depots, hospitals and engineering facilities, as well as other infrastructure closely related to the operation of the battery and the lives of officers and soldiers. By the time World War I broke out, the first phase of Oahu's coastal defense facilities were largely operational.
Four: The second phase of the Oahu Fortress construction
Soon after the construction of coastal defense began, the army turned its attention to defending against possible enemy "rear" landings. The coastal defensive fortresses of Oahu were completely open and completely devoid of defensive infantry capabilities themselves, and the basic idea of defense from 1910 onwards was to fortify all military strongholds to defend against infantry attacks, but due to manpower and financial constraints, the U.S. military soon abandoned this idea and implemented key fortifications only in some locations. Diamond Head Developed into a closed fortress, access to the crater itself can only pass through a tunnel, defenders can control all the local beaches and passages, the U.S. Army in and around the Diamond Head Crater has built a number of artillery positions, with permanent fortifications or field fortifications to block the defensive gap between Diamond Head Hill and the northern mountain, the west side of the mountain behind Honolulu and the hillside protect Pearl Harbor, but in the direction of Pearl Harbor there is a small plain leading inland, however, There is a deep canyon from the Red Mountain to the crater of the Salt Lake, and the U.S. Military has also built an infantry outpost position on the Red Mountain on the side of the canyon, an 83-meter-long and 4.2-meter-wide concrete composite structure bunker, which can accommodate the strength of 2 infantry companies
Ford Island in central Pearl Harbor was a good natural location where flanked land defense guns could be placed to cover the westward defensive line. The U.S. Army built two forts in 1916-1917 to fire to the north and west. The last fortification was located at Bishop's Point on the west side of Fort Kamehameha, two new coastal forts with top protection, two army mobile unit bases were built alongside the establishment of the coastal artillery fort, Fort Shaft was built on a 1,344-acre reservation in the foothills of the Kulau Mountains between Honolulu and Pearl Harbor, and the Schofield Barracks covered an area of 14,000 acres across the landing beaches on the north shore of the island. In 1913 there were about 7.500 troops, consisting of 3 regiments of infantry, 1 regiment of cavalry and field artillery, 8 companies of coastal artillery, and 1 regiment of engineers and signal corps. Fort Shaft was designed to house most of the brigade infantry and field artillery, as well as permanent buildings like the Army's main hospital, quartermaster and ordnance depots would stock the army for 6 months of rations and clothing, and food for Honolulu civilians.
In 1915, the War Department established a new review committee under Commodore Hugh Scott, and the new naval guns equipped by the European Navy had exceeded the range of the 305 mm and 356 mm coastal guns currently deployed by the United States in many port batteries. The Scott Commission recommended the development of a new, larger-caliber coastal gun, culminating in the establishment of two forts at the Kamehameha Fortress. The position was located on newly reclaimed land immediately east of the Kamehamika Fortress Reserve. The gun position consisted of a huge concrete, two gun mounts at each end, with a range of more than 27,000 meters, greatly increasing coverage except for the northernmost beaches of Oahu, and in order to make up for the firepower gap left by the withdrawal of the old artillery, some wheeled and orbital heavy artillery were transferred to Hawaii. At that time, Oahu's main railway line had already surrounded the whole island, which was very beneficial for the use of railway guns. The U.S. military also built some regional railways for railway artillery.
But almost no one has thought about how to defend against the emerging threat of air strikes. The old Taft-era batteries were vulnerable to attack in the air, and even the newly designed long-range batteries exposed the guns, and the only protection was camouflage, because the Hawaiian Islands were beyond the range of any existing aircraft, nevertheless, 14 anti-aircraft batteries equipped with two 76 mm anti-aircraft guns were built at eight locations on the island, most of which were completed in the summer of 1917, although it was not until 1920 that the newly developed M1917 76 mm anti-aircraft guns were installed on these positions. The last improvement to the Oahu fortifications during this period was the construction of a fort with 2 406 mm guns on Cape Iroquois on the west side of the population of Pearl Harbor, and the structure of the new fort was even simpler than that of a long-range battery with 305 mm shore guns, the guns and gun mounts were placed in the open on a cement platform, there was initially no garrison facility, soldiers were transferred from Fort Kamehameha by ship as needed, but eventually a small camp was established.
With the construction of williston Battery, the initial phase of U.S. defense of Honolulu and Pearl Harbor from attack was completed. As far as coastal defence is concerned, these preparations are sufficient, if not overwhelming. The Coast Artillery was more like an elite force at this time, with relatively abundant funds and equipment, and a strong professional team, most of these soldiers were professional soldiers. Due to their long-term enlistment, they are also very familiar with the equipment they use. These units remained unchanged on Oahu, and by the mid-1920s it had become the largest U.S.-operated military base. Founded in 1921 and consisting of four infantry regiments, organic artillery and engineers, the Hawaiian Division was one of the largest and best-equipped U.S. troops of the time, the U.S. Navy also sent aircraft to Oahu, and the land near Fort Kameham was developed into a bomber base and was named Hickam Base in 1934, and between 1907 and 1938 the Army spent about $150 million on the defense of Oahu (twice as much as the naval base itself).
Five: The third phase of the construction of the Oahu Fortress
The U.S. fleet was administratively divided into the Atlantic Fleet and the Pacific Fleet, which anchored on the West Coast, and it was suggested that Pearl Harbor be developed into a first-class base, with the U.S. Navy initially using Honolulu as its Hawaiian naval base before dredging and opening the entrance to Pearl Harbor. In 1900, the U.S. Congress first approved $100,000 for the project to chisel the reef into Pearl Harbor, and after 1909, the dredging of sand and coral heads in the harbor continued. The first warship entered Pearl Harbor in 1911. In 1913, Honolulu Naval Base was transferred to Pearl Harbor Naval Base, and dry docks were completed in 1919. While Pearl Harbor is a good natural harbor, it did encounter some problems, mostly due to the isolation of the island, logistical support. Concerned about the base's lack of self-sufficient food, lack of skilled labor and adequate supply, the Navy has always regarded the base as a good maintenance facility, but due to high costs and the fact that Oahu is not on the main East-West trans-Pacific sea route. Most commercial transport sailed north and east of Hawaii, and initially few ships were permanently distributed to the islands.
By 1938, the main channel to Pearl Harbor had been widened to 1,000 feet and two new dry docks had been added. The naval arsenal, located 15 miles northwest of Pearl Harbor, was completed in 1934. The airport expanded rapidly, and the U.S. Navy chartered EWA Airfield as an air force landing base for the U.S. Marine Corps. Kaneohe Bay on the east coast of Oahu became a seaplane airport. Construction of the Kaneo River Air Station began in September 1939, with Schofield Barracks becoming the army air force's main fighter theater and Ford Island becoming the Navy's main land air base, but it soon became crowded and was replaced by a new naval air station in November 1941. As World War II drew near, the Navy created the Hawaii Detachment, initially consisting of an aircraft carrier, eight cruisers, and 16 destroyers, permanently stationed at Pearl Harbor. In April 1940, the U.S. Chief of Naval Operations sent the Pacific Combat Fleet to the Hawaiian Islands for annual exercises, then decided to keep it at Pearl Harbor, and since the early 1930s the Navy has used the Lahaina Anchorage between Maui and Lanai in northern Oahu as a deep-water anchorage for fleet deployment.
In September 1940, the U.S. military began the construction of the last coastal fortifications. These were thoroughly modern defenses, structures highly standardized and designed to withstand naval and aerial bombardment, and artillery protected by massive concrete and ground coverings. Chemical gas protection was also provided for the new gun positions in the design – airlocks and filters were set up for certain critical areas. The old-fashioned Endicott and Taft batteries would be obsolete until replaced by more modern ones, and as The Caneo Bay developed into a major naval air base, the Hawaii Independent Coast Artillery Brigade began studying this new naval air station and nearby defenses, which also required 90mm and 37mm anti-aircraft guns, searchlights, radar, fire control stations, and harbor defense commands. By the end of 1942, 3 new batteries were built in The Bay of Kaneoch, the new battery numbered 301 was located on a small cliff on the south side of the naval base, and 2 152 mm guns were installed, the outer wall of the fort was 1.8 meters thick and the inner wall was 0.46 meters thick, all made of cement, and the battery command post was located on the top of the ammunition depot and equipped with radar. The ammunition depot was 1.8 meters thick at the top and covered with a 1 meter thick layer of soil, and Gun Turret 302 was built on the surface of the cliff and led by a concrete tunnel to the gun position. There was a tunnel on the hillside behind the gun position number 405, and the three new batteries were not named Hasselburg until the end of the war.
Six: The role of "Oahu Fortress"
In the Pearl Harbor incident, the "Oahu Fortress" did not play any role, the U.S. military invested a lot of time and energy to analyze the nature of the potential threat and how to protect Oahu from the threat, but the defense of the Oahu Fortress was deployed in response to the traditional naval artillery shelling and amphibious landing mode of operation, and its air defense system had obvious flaws, which caused the US military to be defeated in the first battle of the Pacific War, but the US military still believed that the Japanese were likely to return to the landing for several months. Urgent measures were therefore taken to strengthen the island's defences. Coastal artillery units began to disperse to their designated defensive positions. Heavy artillery, fire control stations, and beach fortifications were soon manned, preparing for land that had never been landed, and extreme anxiety, combined with a great deal of rumors and fears about the "Fifth Column" or sabotage operations, must have left the defenders through a period of great confusion.
In the first weeks of the war, many temporary beach defensive positions were in place, all possible landing sites were covered with machine gun positions, barbed wire, infantry trenches and ship obstacles, army and air reinforcements arrived quickly, and the Army's 34th Engineer Corps soon established 10 new positions around Oahu. The Navy soon provided the Army with temporary "borrowed" guns for coastal defense, and also removed the guns from damaged ships for coastal defense, and for a short period of time in 1943, the four turrets of the BATTLESHIP Oklahoma and the four turrets of the USS Arizona were deployed in Cape Macapou in the southeast corner of Oahu and Baomaru on the north shore, respectively, and Cape Kana on the west at Fort Ruger on the south side of the Diamond Head Crater.
Of course, the Japanese did not come, and with the end of World War II, the entire American coastal artillery force entered a period of decline, and the concept of defending the port with fixed artillery became unrealistic due to the lack of immediate threat and changes in technology. The overall drawdown of the U.S. military has had a considerable impact on Oahu's fixed defenses. At the end of the conflict, the rapid reduction in the firepower of the coastal artillery led to the rapid dissolution of the old artillery company at the end of the war, all the remaining fixed coastal artillery was cut to pieces, the fortifications built for the Second World War remained, except for five or six early Taft fortifications and land fortifications, the other fortifications were intact, many buildings were converted for other purposes, many large tunnel complexes built before and during the war still existed, only the entrance can be seen, Because they are either sealed or still in use.