Chapter I
Background

Strategic Situation

By February 1945 American forces had knifed their way across the Pacific and into well buttressed positions along the Luzon-Marianas Line. Admiral Chester W. Nimitz' Pacific Ocean Area (POA) Forces were poised now for a deeper thrust.

Marianas-based B-29's were conducting heavy raids against important industrial and military targets in the Japanese home islands. Southwest Pacific Forces under General Douglas MacArthur were consolidating positions in the Central Philippines and had gained a strong foothold in Luzon. Japanese air power in the Philippines had been crushed and the exhausted Imperial Fleet driven from Philippine waters, leaving the large immobilized land force to wage a stubborn but losing fight.

As never before, the United States had blasted whatever hopes the Japanese held for victory in the Pacific. Moreover, the homeland itself was now in peril.

The relentless precision of the conquests of Saipan, Tinian, and Guam had stunned the Japanese Empire.¹ The initial landing by Central Pacific Forces in the Marianas had precipitated the highly significant naval and air battle of the Philippine Sea on 19-20 June 1944. For the enemy this was a fiasco from which their naval aviation never fully recovered.

The seizure of the Southern Marianas was completed by 10 August 1944, and in September troops of the III Amphibious Corps were occupying positions in the Palau Islands and Ulithi.² The right flank of our line was now secure for operations against the Philippines. (See Map I).

While conducting covering operations preliminary to the assault on the Palaus, Admiral William F. Halsey's Third Fleet had encountered surprisingly light resistance from Japanese land-based air power in the Central Philippines. Sensing that the time was ripe to strike this apparently vulnerable area, Admiral Halsey so informed Admiral Chester W. Nimitz, Commander in Chief, Pacific Fleet (CinCPac).³ Halsey recommended that the projected Yap and Mindanao operations be abandoned, and that troops thus released be made available to Southwest Pacific Forces for an early attack on the Central Philippines. Nimitz concurred in this recommendation and

forwarded it to the Joint Chief of Staff.⁴ Agreement on this plan was reached quickly in a remarkable demonstration of joint action and administrative flexibility.⁵

On 20 October 1944, the U.S. X and XXIV Corps went ashore at Leyte in the Central Philippines, having bypassed Mindanao in the south. The Japanese reacted to this landing just as they had in the Marianas. On 23 October they threw strong naval surface and carrier-based air forces against our vulnerable amphibious shipping in an all-out attempt to smash the invasion before it could commence. The ensuing naval engagement, however, proved disastrous to the Japanese sea power.⁶ By the 26th, our Leyte beachhead was secure from enemy naval intervention.

Leaving the consolidation of Leyte to troops of the Eighth Army, the Sixth Army made a swift amphibious leap to the north and landed on beaches of the Lingayen Gulf in Luzon, 9 January 1945. The fate of the Philippines was now sealed.

The next step was to be an advance from the Marianas through the Bonins to the Ryukyus. This monograph deals with the first step: the amphibious assault on Iwo Jima.

History

Iwo Jima is an infinitesimal piece of land located within the Nanpo Shoto, a chain of islands extending 750 miles in a southerly direction from the entrance of Tokyo Bay to within 300 miles of the Marianas. Comprising the Nanpo Shoto are three major island groups. From north to south these groups are: the Izu Shoto, the Ogasawara Gunto (Bonin Islands), and the Kazan Retto (Volcano Islands). Iwo Jima lies within the third group, some 660 nautical miles from Tokyo.⁷

Detailed early history of the Nanpo Shoto is somewhat obscure. Although Japanese fishermen were familiar with the islands of the Izu Shoto, using them for bases as early as 1500, there is no indication that they operated as far south as the Bonins. A Spanish captain, Bernard de Torres, sighted the Volcano Islands in 1543; yet, despite Spanish activity in the nearby Marianas, it was some 250 years before white men gave attention to islands of the Nanpo Shoto.

The Bonins, however, were discovered in 1593 by a Japanese, Sadayori Ogasawara. This group was found to be uninhabited, and Ogasawara chose to call them munin, meaning "empty of men." Their present popular name, Bonin, is a corruption of that Japanese word.

Beginning a half-century of unprecedented activity, the early 1800's found an increasing number of whaling ships sailing into the waters surrounding the Bonin Islands. Captain Reuben Coffin, of the whaler Transit from Nantucket, landed at Haha Jima in 1823 and claimed it for the United States. Four years later Captain Frederick William Beechey, RN, commanding H.M.S. Blossom, dropped anchor at Chichi Jima and claimed the entire Bonin group in the name of King George IV.

Shortly afterward, as a result of Beechey's visit to Chichi Jima, a strangely mixed company of colonists set out from Hawaii under

the auspices of the British Consul. They settled on Chichi Jima and claimed British sovereignty. This group included Englishmen, Portuguese, Italians, Hawaiians, and one American, Nathaniel Savory of Massachusetts.

Commodore Matthew Perry of the United States Navy stopped at Chichi Jima in 1853. Impressed with the potential importance of the entire Bonin group as coaling stations along the route to China, Perry urged the purchase of a strip of beach at Chichi Jima from Nathaniel Savory--the only remaining white member of the original Hawaiian contingent. Perry's intent was to construct warehouses there dependent on ultimate approval of the United States Government. At that time, however, American foreign policy did not admit Pacific obligations, and the commodore's plan was abandoned.

In the passing of some three hundred years since their discovery, the Volcano Islands and little Iwo Jima did not go entirely unnoticed. An Englishman named Gore had visited this group in 1673 and given Iwo Jima a new name, calling it Sulphur Island for obvious reasons. The next visitor was a Russian explorer named Krusenstern, who came in 1805. Yet not a man who had observed these islands recommended to his parent country that they be colonized.

Some years after Perry's visit of 1853 had opened Japan to the west, the Japanese dispatched two officials with 40 colonists to hold the Bonins for Japan. They renamed the islands "Ogasawara" and based their claims on the assumption that they had been discovered by Sadayori, Prince of Ogasawara, in 1593. In 1861 the Japanese made formal claim to the Bonins and were never seriously challenged.

In 1887 the Japanese started colonizing the Volcano Islands and by 1891 had incorporated them into the Ogasawara Branch Administration. Thereupon, all the island of the Nanpo Shoto came under the jurisdiction of the Tokyo Prefectural Government and were administered as an integral part of Japan. Never very strong, American and European influence in this area died out almost entirely. With increased Japanese colonization in the early 1900's and a ban on foreign settlement, the entire Nanpo Shoto became completely Nipponese. On Chichi Jima, however, descendants of Nathaniel Savory and the other original settlers, who called themselves "Bonin Islanders," celebrated Washington's Birthday and the Fourth of July each year by displaying Old Glory and refused to associate with individuals of Japanese blood.⁸

NO TRESPASSING sign dated 1937 indicates Japanese attitude toward visitors at Iwo.

The civilian population on Iwo Jima numbered 1,091 in 1943, all of whom were of Japanese descent. These people were centered in and around Motoyama, Nishi, Kita and Minami. Their homes were typically Japanese--flimsy one-story frame dwellings, often built a foot off the ground. Livelihood was derived from working in a small sugar mill and a sulphur refinery. Small scale agriculture was carried on, with vegetables, sugar cane, and dry grains being grown for local consumption. Although rice was a staple, it had to be obtained from the homeland, as did all manufactured articles needed for a bare existence. The Iwo inhabitants also fished to piece out their meager diet.

AERIAL VIEW illustrates pork chop shape of Iwo Jima.
Suribachi, in right foreground, is at southern end of island. (Navy Photo)

In the main, potable water was obtained by catching rain in concrete cisterns.⁹

Geography

The island of Iwo Jima lies slightly south and west of the midpoint of a line drawn between Tokyo and Saipan: 625 nautical miles north of Saipan and 660 miles south of Tokyo. Viewed from the air this desolate looking piece of land resembles a pork chop, while in profile from the sea it has the appearance of a half-submerged whale. An extinct volcano, Mount Suribachi, forms the narrow southern tip of the island and rises 550 feet to dominate the entire area. Suribachi is linked to a dome-shaped northern plateau by land that fans out broadly to the north and northeast. The entire island measures only 4²/3 miles along its northeast-southwest axis, while the width varies from about 2½ miles to slightly less than one-half mile at the narrow base of the volcano. The surface area of Iwo Jima is 7½ square miles. (See Map II.)
Map II -- Iwo Jima (Sulphur) Island

The "shank" of the island between Suribachi and the plateau is covered with a deep layer of

coarse, black volcanic ash. The particles of grit are light enough to be shifted by the wind. Progress over this soft, drifted surface is difficult both on foot and in vehicles.

The northern plateau is roughly one mile in diameter and the ground sloping to the coast from this elevation is rough, steep, and broken by rocky cliffs. The plateau itself is interlaced with chaotic gorges and ridges, the elevation being between 340 and 382 feet. Here the ground is rough and rocky, a jumble of scarred stone, with scattered clearings in the rock. In many places the ground is hot. Steam hangs in ghostly veils over the gray-brown sulphur vents that emit their characteristic fumes.

From the northern tip, Kitano Point, along the shoreline for a distance of about two miles southeastward to Tachiiwa Point, the beach is narrow and steep with many rocky shoals obstructing approach. Just behind these northeastern beaches the ground rises sharply to the northern plateau with few beach exits. The remainder of the northern coast is rough, with abrupt cliffs ascending directly from the water's edge.

To the south, on either side of the narrow part of the island, the beaches are generally unobstructed by offshore rocks and vary from 150 to 500 feet in depth. Sand terraces of varying heights and widths hinder movement inland even for tracked vehicles. These terraces are caused by perpetual wave action and tend to change from time to time in size and location. Violent storms cause radical changes.

Surf conditions at Iwo, even in normal weather, are difficult for all classes of landing craft. There is no anchorage or protected area, and ships must discharge their cargo into lighters to be transferred to the shore. The steep beaches cause the waves to come close inshore before breaking, so that most of their force is expended in a downward blow on the bows of incoming or beached small boats. An onshore wind greatly increases the severity of the surf, often making unloading on the windward side of the island precarious.

Because Iwo lies just north of the Tropics (24° 44' north latitude--141° 22' east longitude), the weather is subtropical, with a cool season lasting from December through April and a hot season from May through November. Average temperatures range from 63° to 70° in the cool period to 73° to 80° during May-November. Annual rainfall averages 60 inches; February is the driest month and May the wettest. The path of Pacific storm centers includes this area from December through June and although the normal typhoon track passes to the north, Iwo is a typhoon danger area.

An absence of potable water supply, other than rain, presents an acute problem. Since the soil and rocks are highly permeable, use of cisterns remains the only effective means to catch and retain the rain. Distillation of sea water and the occasional use of tankers supplement the supply.

Natural cover on Iwo Jima is sparse. So sterile is the soil that coarse grasses and gnarled bushes and trees appear in a constant struggle to exist. Major Yokasuka Horie, Imperial Japanese Army, writes of Iwo: ". . . But we had no special products on this island and it had been written on the geographical book as only an island of sulphur, no water, no sparrow and no swallow. . . ."¹⁰

Such was Iwo Jima: so economically insignificant as to be largely unknown even to the Japanese, yet having a potential strategic importance of such magnitude that it became the most heavily fortified and stubbornly defended real estate in the Pacific.¹¹

Japanese Preparations

Military activity in the Volcano-Bonin Islands area began in 1914 when the Japanese General Staff decided to fortify Chichi Jima.

A small amount of heavy artillery was emplaced, and in 1917 a naval radio station and a weather station were established. No major development was attempted, however, and in 1941 when hostilities between Japan and the United States broke out the total Japanese garrison in the area was only about 1,400 men, all on Chichi Jima. A naval force of about 1,000 manned the Chichi Jima Naval Base and a small seaplane base in addition to the radio and weather stations. The army garrison consisted of a Fortification Headquarters and one company of about 400 men under command of the Eastern Army Headquarters in Japan.

In 1943 the major portion of the Japanese military strength in the Volcano-Bonin Islands area was still located at Chichi Jima, but the army strength had increased to about 3,800 men. Chidori Airfield (Airfield Number 1) had been constructed on Iwo Jima, and about 1,500 naval air force personnel with 29 planes were stationed there.

With the invasion of the Marshalls, early in February 1944, followed by the crippling strikes against Truk in the same month, it became clear to Japanese Imperial Headquarters that the Marianas-Carolines area was threatened. Steps were taken to strengthen the defenses of the "inner line" (Carolines, Marianas, and the Volcano-Bonins), and in March the 31st Army was organized with its headquarters on Saipan and charged with the responsibility for the over-all defense of the area. The Chichi Jima Fortress Commander was ordered to take charge of all army and navy units in the Volcano-Bonin Islands.

During March and April the army-navy buildup on Iwo began in earnest. Some units were sent from Japan directly to Iwo while others were transferred there from Chichi Jima. A naval guard force was organized with about 500 men from Chichi and another 500 from the Yokosuka Naval Base, and this unit was given the responsibility for fixed antiaircraft and coast defenses on the island.

By the end of May 1944 army strength on Iwo was listed as 5,170 men, 143 artillery pieces, 0ver 200 light and heavy machine guns, and 4,652 rifles. In addition, 14 coast-defense guns of 12cm or larger, 12 heavy antiaircraft guns and 30 25mm twin-mount antiaircraft guns¹² were operated by the Iwo Naval Guard Force. This buildup was not without some friction, however, and the commanding officer of the Iwo Jima Guard Force sounded a note of warning when he wrote:

On this narrow island where water and other necessities of life are very scarce, there are concentrated over 7,000 Army and Navy personnel. If the Army and Navy are especially careful to act as one harmonious unit, there will result a determination which will increase the fighting strength on this island.¹³

Late at night on 13 June the troops on Iwo were alerted to the fact that Saipan had been under heavy attack by naval forces. On 15 June "Condition 1" was set on Iwo, and by the time the men had reached their shelters a dogfight was in progress overhead and dive bombers pounded the airfields. Those not busy manning the antiaircraft guns watched this show with awe. The American pilots soon had complete control of the skies, and one Japanese witness told his diary, "Somehow, my faith in Navy air groups has been somewhat shaken."¹⁴

When United States troops seized Saipan the headquarters of the Japanese 31st Army fell with the island, and Imperial General Headquarters in Tokyo reorganized the command structure for their dwindling island holdings. On 26 June the enemy high command sent out an order removing troops in the Volcano-Bonin area from the 31st Army and placing them under direct control of headquarters in Tokyo.¹⁵ By the end of June a new command, the 109th Infantry Division, had been organized, with

headquarters on Iwo, and entrusted with the defenses of the area.

LIEUTENANT GENERAL KURIBAYASHI,
Senior Japanese officer on Iwo, planned and directed astute defense of the island.

Troops and equipment that had been hastily assembled in Japan for the relief of Saipan were now reassigned to the 109th Division, and Japanese planners concerned themselves with making Iwo Jima impregnable.¹⁶ The emphasis had switched from Chichi Jima to Iwo Jima because it was the only island in the area suitable for airfield construction. Chichi Jima's importance from this time on lay only in its function as a supply base for Iwo, and the 109th Division maintained a "detached headquarters" there for the express purpose of handling supplies.¹⁷

With American planes and submarines harrassing convoys, the task of reinforcing Iwo Jima was not easy.¹⁸ Most shipments were sent first to Chichi Jima where ships were unloaded at night as protection against air attack. Material destined for Iwo was loaded into smaller craft for the final perilous 150-mile leg of the journey. Cargo and troops making the trip direct to Iwo from Honshu were carried in destroyers or light high-speed transports. Air attacks, rough seas, and the lack of harbor facilities combined to make unloading at Iwo difficult and hazardous.

An idea of the difficulties involved in reinforcing Iwo can be drawn from the experiences of the 26th Tank Regiment as related by Superior Private Hisao Nakada of the 3d Company. His regiment was in Manchuria during all of 1943, but in April of 1944 the unit received orders to proceed to Saipan. After a reorganization, the regiment left Manchuria, but by the time it reached Pusan, Korea, news of Saipan's fall arrived and it was ordered to Iwo. Upon reaching Japan, all but one company and 13 tanks of the regiment embarked in the Nisshu Maru and sailed from Yokohama on 14 July. When only 30 hours out from Chichi Jima the ship was struck by two torpedoes and sank in about half an hour. Most of the personnel were rescued and taken to Chichi, but the 28 tanks were lost. In August, 46 men from the regiment returned to Japan for replacement tanks, but, for reasons unknown, it wasn't until 18 December that they left Yokohama with 22 tanks, arriving at Iwo on 23 December. Before they could be unloaded, three of these tanks were destroyed during a naval bombardment of the island.¹⁹

MAJOR GENERAL SENDA
commanded 2d Mixed Brigade, the major army unit on the island.

In spite of these difficulties, during the 3-month period from June through August of 1944, fighting strength on Iwo more than doubled. Additions during this period numbered more than 9,600 troops: 7,350 army and about 2,300 navy.

The 109th Infantry Division was commanded by 53-year-old Lieutenant General Tadamichi Kuribayashi. Kuribayashi had seen combat in Manchuria in 1938 and 1939 as a colonel commanding the 7th Cavalry Regiment. In 1940 he was promoted to Major General (the lowest general office rank in the Japanese Army) and given command of the 1st Cavalry Brigade. He was transferred to the Canton area in 1942 where he served as Chief of Staff of the 23d Army. In 1943 he was called to Tokyo to reorganize the Guards Brigade into the 1st Imperial Guards Division.

While on duty in Tokyo he attained the ambition of every Japanese when he was given the singular honor of an audience with the Emperor. In June 1944, he went to Iwo Jima and a rendezvous with death and renown. A Japanese major captured on Iwo revealed that the general was ". . . sternly disciplined and very strict with his subordinates . . . the troops disliked the general possibly because of these very attributes." During the fighting for this island Radio Tokyo described him as a man ". . . . whose partly protruding belly is packed full of strong fighting spirit."²⁰

The major army units of Kuribayashi's command on Iwo were the 2d Mixed Brigade commanded by Major General Sadasue Senda,²¹ Colonel Masuo Ikeda's 145th Infantry Regiment, and the 3d Battalion, 17th Mixed Infantry Regiment under Major Tamachi Fujiwara. All the artillery on the island was organized into a Brigade Artillery Group under Colonel Kaido. This included the artillery battalion of the 2d Mixed Brigade, the 145th Infantry's artillery battalion, the 1st and 2d Medium Mortar Battalions, and the 20th Independent Artillery Mortar Battalion.²² The Brigade was reinforced further by five independent antitank battalions, the remnants of the 26th Tank Regiment,²³ two independent machine-gun battalions, and three rocket companies.²⁴

Over-all command of the naval forces fell to Rear Admiral Toshinosuke Ichimaru, the senior naval officer on the island and one of the foremost airmen in the Japanese Navy. He was commanding officer of the 27th Air Flotilla, a joint command with the 2d Air Attack Force of the Eastern District (Tokyo Area), under the 3d Air Fleet. The next ranking naval officer was Captain Samaji Inoue, also a naval airman, who commanded the Nanpo Shoto Naval Air Group. In October, Captain Inoue was given

REAR ADMIRAL ICHIMARU,
senior naval officer on Iwo, was one of Japan's foremost airmen.

additional duties as Commander of the Iwo Jima Naval Guard Force. The 204th Naval Construction Battalion, composed of Japanese, Koreans, and about 400 natives of Iwo, was commanded by Lieutenant Fujiro Iida. During 1944 a second airfield (Motoyama) became operational and construction was begun on a third field north of Motoyama. Airbase Unit Number 52 operated these fields for the planes of the 901st Air Group, the 252d Air Group, and the 2d Independent Army Air Unit based on the island.

For defense, all naval units other than the coast defense and antiaircraft batteries of the Naval Guard Force were organized into the Naval Land Force and trained and equipped for infantry action. Aviation specialists and ground crews were integrated with the construction battalion personnel in this defensive setup. As commanding officer of the Nanpo Shoto Naval Air Group and the Naval Guard Force, Inoue commanded this Land Force.²⁵

The chain of command was quite complicated. Nominally, all army forces were under General Kuribayashi and all naval forces under Admiral Ichimaru, but actually there were three major headquarters operating more or less autonomously. These were the headquarters of the 109th Division, the 2d Mixed Brigade, and the Naval Land Force. In addition, the island was divided into five defense-sector subcommands with one army battalion (plus supporting units) commanded by the senior army officer in the sector. Also in each sector was one group of naval troops independently commanded by the senior naval officer of the sector. While there was not real unity of command in such an organization, Kuribayashi and Ichimaru "cooperated" and directed their subordinates to do likewise.²⁶

The five defense sectors with troop allocations as indicated on a captured map were as follows:

Sector	Troops
Mount Suribachi Sector	312th Ind. Inf. Bn. (Army), AA and CD Units (Navy).
Southern Sector	309th Ind. Inf. Bn. (Army), Naval Land Force Unit.
Western Sector	311th Ind. Inf. Bn. (Army), 1st Co., 26th Tank Regt. (Army), Naval Land Force Unit, AA and CD Units (Navy).
Eastern Sector	314th Ind. Inf. Bn. (Army), 3d Co., 26th Tank Regt. (Army), AA and CD Units (Navy).
Northern Sector	3d Bn., 17th Ind. Mixed Regt. (Army), 2d Co., 26th Tank Regt. (Army), Naval Land Force Unit, AA and CD Units (Navy).27

Although not assigned to a defense sector by any of the Japanese documents found on the island, the 1st Battalion, 145th Infantry occupied the area of Airfield Number 1.²⁸ (See Map 1.)

Map 1 -- Japanese Defense Sectors

In drawing up early plans for the defense of Iwo, Kuribayashi and his staff recognized that the naval surface and air power thrown against them would make positions on the beaches and around Airfield Number 1 untenable. Their plan, therefore, called for fortifying the Mount Suribachi and Motoyama Plateau districts, holding the beaches lightly but covering them by fire from the high ground. They would also have a large reserve force, including tanks, to counterattack and drive the invader back into the water should he gain a foothold.

Naval tacticians, however, held to the idea that the beach must be heavily defended and the decisive combat joined with the enemy at the water's edge. To this end a naval staff officer from 3d Fleet Headquarters visited Iwo to champion their cause. He urged that the navy be permitted to construct pillboxes on the east and west beaches and in the vicinity of Airfield Number 1. The army was far from enthusiastic about this plan of action, but in August Kuribayashi decided to permit the navy to construct the positions and designated one infantry battalion to man them.²⁹

By January 1945 Kuribayashi had modified his concept of the defense.³⁰ His new plan was simple and well adapted to the terrain and size of the island. In a departure from traditional Japanese defensive doctrine he abandoned the idea of all-out counterattacks against the beachhead and costly banzai charges. Instead, strong, mutually supporting positions were to be occupied prior to D-Day and defended to the death. Large-scale counterattacks or withdrawals were not planned.

The Mount Suribachi area was made a semi-independent defense sector, its heavily fortified positions bristling with weapons of all types, ranging from casemated coast-defense guns and artillery to automatic weapons emplaced in mutually supporting pillboxes. The narrow isthmus connecting Suribachi to the rest of the island was lightly held by infantry, but heavily defended by enfilade fire from artillery, rockets, and mortars emplaced on both the high ground in the south (Suribachi area) and the northern portion of the island.

The main defense line was a belt of mutually supporting positions organized in depth, running generally northwest-southeast across the island. It stretched form the cliffs north of the western beaches south to include Airfield Number 2; then, turning eastward through Minami, terminated at the rugged coast north of the eastern beaches. Pillboxes, blockhouses, bunkers, and dug-in tanks strengthened the defenses in the naturally formidable terrain everywhere throughout this belt.

The second defense line generally bisected the remaining area in the northern portion of the island. It began several hundred yards below Kitano Point on the northwest coast, cut through Airfield Number 3 and the Motoyama area in the center, and terminated between Tachiiwa Point and the East Boat Basin on the eastern coast. Man-made emplacements were not as numerous in this second line, but natural caves and other covered positions afforded by the fantastically rugged terrain were skillfully organized for the defense.³¹

It is believed that this positional defense was Kuribayashi's own personal solution and was adhered to despite the contrary advice of Colonel Horie, his Chief of Staff.³²

Although Kuribayashi's final plan of defense was basically static, the training annex to his operation order dated 1 December 1944, made it clear that he did not intend it to be entirely without movement and aggressive counteraction. He directed that troops occupying "main positions" should be trained for small unit counterattacks in front of cutoff positions, and that reserves should practice counterattacks and "movements inside positions," stressing cooperation with the artillery. He also emphasized

the training of tank units for participation in counterattack.³³

The artillery plan was the brain child of Colonel Kaido, the Artillery Group Commander. In it he assumed that the attackers would have more artillery than the Japanese and stated that counterbattery duels should be avoided; but he added that full fire power should be used in an attempt to destroy enemy tanks. Detailed plans were made for displacement of observation posts and firing positions to secondary positions. As a general rule there was to be no adjustment of artillery fire as practiced by United States artillery units, and emphasis was given to surveys and preregistration fires. Airfields were mentioned repeatedly as important targets. A part of the firepower was to be prepared to cover each airfield in the event of landings by airborne forces.³⁴

Dispersal and concealment were stressed:

We must strive to disperse, conceal, and camouflage personnel, weapons and material, and make use of installations to reduce damage during enemy bombing and shelling. In addition we will enhance the concealment of various positions by the construction of dummy positions to absorb the enemy shelling and bombing.³⁵

A reserve force was held out "to take part in the long term resistance."³⁶

Although the army exercised operational control over all artillery on the island, antiaircraft

127MM DUAL-mount antiaircraft guns protected the airfields. (AF Photo)

artillery was under the operational control of the navy. As the commanding officer of the 109th Division Antiaircraft Artillery Unit wrote in his battle plan:

The Iwo Jima AA Arty Unit will be under the single command of the Naval Guard Unit Hq for combat purposes and will cooperate with the other Naval Forces.³⁷

The logic of this control is obvious when it is considered that more than three-fourths of the antiaircraft guns were naval. Moreover, Naval Guard Force units had originally been charged with responsibility for the antiaircraft defenses of Iwo. A large number of these weapons were emplaced to fire not only in their primary role but also to engage ground targets.

The Japanese defenders had 46 artillery pieces of 75mm or larger, including 12 artillery mortars of 320mm; 65 medium and light mortars (150mm and 81mm); 33 naval guns (80mm and above), many of which were dual purpose; 94 antiaircraft guns 75mm or larger, and over 200 20mm and 25mm antiaircraft guns. To this should be added 69 37mm and 47mm antitank guns and the 37mm and 57mm guns of the 12 light and 12 medium tanks on the island.

In addition to previously mentioned weapons, there were at least three different rocket-propelled projectiles. The largest was a 250kg (550-pound) bomb, less tail assembly, with rocket motor attached. Fired from a launching trough 22 feet long, it had a range of better than 7,500 yards. Similar, but smaller, was the 63kg bomb with rocket motor. Launching troughs for this projectile were from 13 to 15 feet in length, and its maximum range was about 2,000 yards.

The navy had a spin-stabilized 8-inch rocket weighing about 200 pounds with a range of 2,000 to 3,000 yards. This projectile was converted from a naval 200mm shell by cutting it off forward of the rotating band and threading it to receive a base plate and rocket motor. It was fired from a stovepipe-like barrel mounted on a steel carriage equipped with two wheels, giving it mobility. The three army rocket companies on Iwo were probably equipped with the 63kg rocket-propelled bombs.³⁸

The 320mm (spigot) mortars of the 20th Independent Artillery Mortar Battalion were crude and unusual. This defensive weapon consisted of a solid steel cylinder with a cavity in the upper end, seated on a steel base plate secured to a platform of wooden beams. For firing, the 320mm projectile (5-feet long, 12.8-inch diameter) fitted around and over the 250mm cylinder (31.7 inches long, 10.1 inches in diameter). The maximum range of this weapon was 1,440 yards with traverse of 20° to either flank, range adjustment effected by quantity of the charge. Deflection changes were made by the mortar crew shoving and pulling the ponderous platform by hand. This rather bizarre weapon had a life of only five or six rounds and this, plus constant fear of dropping the 675-pound shells on their own men, limited training of the gun crews.³⁹

The Japanese active defense against United States air raids was only moderately successful, but passive defense measures were so effectively carried out that enemy fighting strength was conserved almost intact. As American bomber raids increased in intensity and frequency the Japanese dug deeper and camouflage discipline tightened.

An elaborate system of caves, concrete blockhouses, and pillboxes was commenced soon after the fall of Saipan, and construction work continued right up until the time of the Marines' landing. Blockhouses and pillboxes near the beach were sited to deliver flanking fire. These pillboxes were constructed of reinforced concrete with walls as much as four feet thick, and with sand piled as high as 50 feet in front of some of them for additional protection, leaving only a narrow fire lane. This construction sacrificed fields of fire for protection, but the number of such structures made up for this limitation.

320MM SPIGOT MORTAR showing steel cylinder, base plate, and wooden platform.

In spite of a shortage of cement and reinforcing rods throughout enemy-held islands in the Pacific, Iwo received a large quantity of these items. After several Japanese defeats and island losses in late 1944, supplies intended for other garrisons were routed to Iwo, including vital building materials.

The main communication center for maintaining contact with Imperial Headquarters was a large blockhouse of reinforced concrete located just south of Kita. The roof was ten feet thick and the walls five feet. This fortress contained a single room 150 long and 170 feet wide that housed about 20 radios with one

operator for every two or three sets. The entrance was a 500-foot tunnel about 75 feet underground with the tunnel opening located between small hills.⁴⁰

Natural caves were improved, their entrances camouflaged and so planned that shelling could not hit them directly. From small caves that could accommodate only a few men, they ranged in size to some large enough to accommodate 300 to 400. Most of them were provided with multiple entrances to permit escape. The man-made caves were 30 to 40 feet deep and complete with stairways, interlacing corridors, and passageways. The brigade headquarters, located about 800 yards east of Airfield Number 2, consisted of circular tunnels capable of sheltering 2,000 troops. Further tunneling was planned to connect this cave installation with the command posts in the several defense sectors.

The alternate command post for the Naval Land Force and the 109th Division CP were dug in the northern part of the island about 500 yards northeast of Kita. Because of hard ground and sulphur fumes, the men had to work in shifts and were expected to dig three feet during a 3-hour shift. Construction continued "round the clock:" three hours on and five off, but if workers did not accomplish the allotted three feet, they were required to dig until completed. In one place the ground was so hot that the Japanese could cook a pan of rice in 20 minutes.⁴¹

A Japanese account mentions a plan to dig an underground passageway (total length 38,000 meters) to connect all the various defense sectors. About 25 percent of the garrison was employed daily in these projects. The work was extremely tiring, and workers were only able to labor form five to seven minutes at a time, wearing gas masks because of the sulfur fumes. Only 5,000 meters of the passageway had been completed when the American troops landed on Iwo Jima.⁴² A captured survey sketch of the air defense shelter plan of the Suribachi sector, covering about half of the northern slopes, shows the lower portions of these honeycombed with tunnels connecting gun positions, observation posts, and command posts. Entrances were in close proximity to storage areas and ammunition dumps. In this one section the sketch shows more than 7,000 yards of tunneling.⁴³

To protect the airfields, antitank ditches were prepared in a broken line of segments 20 to 30 feet in length with 20-foot intervals between trenches. In this, as in other phases of the construction of defenses, excellent use was made of the terrain. Natural tank routes were mined, with and without pattern. Extensive use also was made of antipersonnel mines and booby traps in these mined areas.⁴⁴

Not all construction effort was expended on fortifications. Men and equipment were kept busy in large numbers repairing airfield damage caused by the B-24 raids. Typical were the activity of 624 men, 11 trucks, three rollers, and two bulldozers employed in repairing Number 1 Airfield after a raid by 14 B-24's on 2 January 1945. Twelve hours were required to put the field back into operation. This work interfered with fortification and training, but it was necessary.

United States air and submarine attacks on Japanese shipping were making it increasingly difficult to supply Iwo by surface craft. Logs kept by the Nanpo Shoto Naval Air Group Transport Office indicate that many items normally supplied by ship (such as food, automotive parts, and munitions) were flown in. The log makes repeated reference to mortar shells and shows that, during the few weeks just prior

to the invasion, air shipments of armor-piercing shells were received.⁴⁵

At this time Iwo was also used as a base to stage planes from Kisarazu, Honshu for attacks on Saipan. A captured list of planes using Airfield Number 1 indicates that the last such flight consisted of two planes that landed on 3 January. There is no time of departure shown, however, and the following note appears in the log: "Both planes were defective and the attack was abortive."⁴⁶

Kuribayashi's primary mission was to defend Iwo, and he became somewhat impatient with the expenditure of time and effort in airfield construction. While he must have been keenly aware of the importance of the existing fields and their maintenance, he expressed himself rather strongly on the subject:

Long period of time and enormous number of men used for the extension work of the first and "Motoyama" airfield have impeded the defense, fortification, and drill greatly.

We must avoid constructing hopeless airfield.⁴⁷

Training was not neglected. Colonel Kaido's artillery group conducted extensive maneuvers and exercises during November. In his critique Kaido commented on all phases of the maneuvers. The following remarks are quoted as being of special interest:

It is neccesary to eliminate completely the idea that firing results are satisfactory if shells merely fall in the enemy area. We must without fail score direct hits on the targets. On this island, where the amount of ammunition is small and there is no hope of replenishment, this is especially true. Accordingly, it is necessary to perfect the various activities of the gun crews and observation and communication [personnel], as well as firing preparations and fire control.

Protection and camouflage are still incomplete. This is particularly true of embrasures, covered gun positions, observation posts, and entrances.

The dispersion and location of ammunition dumps is good, . . . but they might easily be damaged by shells landing nearby.

It is necessary to rush the construction of reserve positions and OP's and to make plans for facilities for moving to reserve positions.

It is desirable that attention be given to the prevention of dust in front of gun muzzles. Some arrangements such as spreading straw matting or sprinkling water must be made.⁴⁸

In his operations order of 1 December, Kuribayashi directed all units to ". . .  plan for absolutely thorough training and for further strengthening of fortifications." He instructed that existing fortifications should be tested as to practicality and improved when found lacking:

Matters to be kept in mind when considering improvements in existing fortifications are as follows:

1. Increasing AT obstacles, such as ditches, terraces, obstructions (piles of rocks).

2. Strengthening connecting and escape trenches.

3. Establishment of "waiting" trenches for use in close combat and raiding.

4. Setting up of combat installations for the defense of billeting areas.⁴⁹

Setting 11 February as the deadline for completion, he specified that 70 percent of the time should be devoted to training and 30 percent to fortification.

The major personnel buildup was effected by the middle of 1944, but reinforcements continued to arrive until February 1945. Early in 1945 rumors among the troops suggested that the Japanese Army promised no further aid to Iwo and that it was up to the defenders to repulse any major landing attempt with the men and materials at hand, or to hold out as long as possible. There was more optimism, however, in the belief that the navy would resist strenuously any United States fleet venture into the Volcano-Bonin area.

Morale was good, although there were malcontents who complained about the food and lack of beer, sake, and women, and the general

WOODEN ROCKET LAUNCHERS like this were found after Marines landed. (AF Photo)

dreariness of life on this desolate outpost. A feeling of hopelessness and pessimism as to the outcome of the inevitable battle was countered by the resolve to fight bitterly to the end and die gloriously for the Emperor.

On 14 February Admiral Marc A. Mitscher's Fast Carrier Force (TF 58) was detected moving north. Interpreting this as a sign of impending assault on Iwo Jima, Army Group Headquarters ordered all units into the D-Day positions. The 1st Battalion of the 145th Independent Infantry Regiment moved into positions in the vicinity of Airfield Number 1, and other units left their bivouacs to take over their battle assignments. When the landing seemed imminent, the chief of staff of the garrison force issued the following order:

All units, especially headquarters, will take the utmost precaution not to let our tables of organization, tables of equipment, strengths or very secret documents be compromised. Even persons in Headquarters must keep them to themselves and not let them be passed to the enemy.⁵⁰

Another captured document stated that certain key officers in the Iwo Jima Naval Guard Force were to be responsible for the destruction of all classified documents when so ordered by the highest naval command, or when it was apparent to the custodian that such destruction was necessary.⁵¹ These instructions revealed a growing security consciousness among the Japanese.

Final preparations were hastily made. Time was precious, and much remained to be done. Camouflage had to be repaired, mines armed, and positions strengthened. On 17 February, word was passed to complete demolition of roads. At about 1030 the Japanese in the East Boast Basin area observed "twenty-odd large and small landing craft . . . approached as if to land." The description of this incident from a Japanese diary is given below:

The position of myself and my buddies is untenable. We were immediately posted to our positions to make preparations for an attack, and at the same time our artillery laid down a fierce barrage. At first, both sides were firing and the continuous smoke and noise of the explosions were terrific. This lasted for 30 minutes after which the enemy without attaining its objective moved the attack to the west coast. The enemy made all of this sacrifice without attaining any results.⁵²

The same day the chief of staff issued the following instructions:

The time has come for the enemy to direct his attack upon the Ogasawaras. I fervently desire you and your unit who are charged with the defense of the first line to heroically fight with absolute confidence.⁵³

Kuribayashi himself expressed his feelings in these words:

All shout Banzai for the Emperor! I have utmost confidence that you will all do your best. I pray for a heroic fight.⁵⁴

Table of Contents ** Previous Chapter (Foreword/Preface) * Next Chapter (2)

Footnotes

1. Maj C.W. Hoffman, Saipan: The Beginning of the End, and The Seizure of Tinian; Major O.R. Lodge, Recapture of Guam, MarCorps Historical Monographs (U.S. Government Printing Office, 1950, 1951, and 1954).

2. Maj F.O. Hough, The Assault on Peleliu, MarCorps Historical Monograph (U.S. Government Printing Office, 1950).

3. Nimitz was also Commander in Chief, Pacific Ocean Areas (CinCPOA).

4. Maj C.W. Boggs, Jr., Marine Aviation in the Philippines, MarCorps Historical Monograph (U.S. Government Printing Office, 1951), hereinafter cited as Boggs.

5. Biennial Report of The Chief of Staff of the United States Army, 1Jul43 to 30Jun45, 71-73.

6. A report by the Joint Intelligence Subcommittee of the Combined Chiefs of Staff called, "Possibility of Japanese Withdrawal from the Outer Zone," (London, 8Dec44) states in part:

As a result of their misguided intervention in the Philippines, the effective strength of the Japanese major naval units has now been reduced to 4 battleships, 3 fleet and converted operational carriers, 2 escort carriers, 7 heavy cruisers. Repairs to damaged ships may increase this strength within the next few months by 2 battleships, 2 carriers and 7 heavy cruisers. In addition 2 new fleet carriers may be ready.

Although the 2 battleship carriers and some effective cruisers are still in the South China Sea Area, the Japanese Navy is unlikely again to intervene in strength until the allies launch their final assault on Japan. Japanese Naval policy will be to conserve their remaining strength for the defense of the Inner Zone.

7. Shoto is a Japanese word meaning chain of islands; Gunto, several islands in a group; Retto, several islands in a line; Shima or Jima, an island. Iwo is a Japanese word meaning Sulphur. Kazan means volcano.

8. Interview Maj J.N. Rents with author 29Nov51.

9. The foregoing account of the historical background is a synthesis of the following sources: CinCPac-CinCPOA Bulletin No. 126-44 (August 1944); Osborn, The Pacific World (New York, 1944), 157-159; Encyclopedia Britannica, articles "Ogasawara Jima" and "Volcanic Islands"; F.R. Dulles, America in the Pacific (Boston and New York, 1932), 68-73; T. Terry Terry's Japanese Empire (Boston and New York, 1914), 105-106; W. Price, Japan's Islands of Mystery (New York, 1944), 31-36.

10. Y. Horie, "Explanation of Japanese Defense Plan and Battle of Iwo Jima," Chichi Jima, 25Jan46, hereinafter cited as Horie. Maj Horie, a staff officer of the Japanese 109th Division (commanded by LtGen Kuribayashi), was commanding officer of the Chichi Jima Detached Headquarters.

11. The foregoing section on geography is a synthesis of the following sources: CinCPOA Joint Staff Study, DETACHMENT, 7 Oct 44, hereinafter cited as DETACHMENT; Intelligence Section, Amphibious Forces Pacific "Information on Iwo Jima (Kazan Retto)," undated; Assistant Chief of Staff, G-2, U.S. Army Forces, Pacific Ocean Areas, "Study of Iwo Jima," undated.

12. CinCPac-CinCPOA Item No 9652 "A Report from the Chief of Staff of the 31st Army to the Chief of Staff, Central Pacific Fleet," a Japanese report dated 31May44.

13. CinCPac-CinCPOA Item No. 9512, "Report on Present Conditions by Iwo Jima Guard Unit Commander." Unless otherwise cited, material contained in the preceding section was based on the following sources: CinCPac-CinCPOA Bulletin No 2-46, 15Feb46, "Field Survey of Japanese Defense on Chichi Jima Retto," 5; Fifth Amphibious Corps C-2 Study of Enemy Situation, 6Jan45, 1-3, hereinafter cited as VAC C-2 Study.

14. CinCPac-CinCPOA Bulletin No 161-45, 27Jun45, "The Japanese on Iwo Jima," extracts from a series of diaries, 2May44-11Mar45, hereinafter cited as Japanese Extracts.

15. VAC C-2 Study, 7.

16. One desperate solution advanced involved complete destruction of the island to keep it out of enemy hands. Major Y. Horie voiced this plan as follows: "Now we have no fleet and no air forces. If American forces will assault this island it will fall into their hands in 1 month. Therefore it is absolutely necessary not to let the enemy use this island. The best plan is to sink this island into the sea or cut the island in half. At least we must endeavour to sink the first airfield." Horie, 4.

17. Horie, 5; CinCPac-CinCPOA Bulletin No 2-46, 15Feb46.

18. A Japanese source states: "The number of ships damaged by enemy submarines and planes gradually increased after August 1944, especially in the area between Chichi Jima and Iwo Jima. Over 1,500 persons were killed and over 500 tons of supplies lost." Japanese studies in World War II, No. 61, "Operations on Iwo Jima," hereinafter cited as Japanese Studies.

19. CinCPac-CinCPOA Bulletin No 17-45, 7Jul45, 139. Another example is the 17th Mixed Regiment, which left Japan for Iwo in July 1944. The ship that carried the 1st and 2d Battalions was sunk and the survivors taken to Chichi. The 3d Battalion reached Iwo but was never joined by the other two. CinCPac-CinCPOA Bulletin No 2-46, 15Feb46, 5.

20. This thumbnail sketch of Kuribayashi is based on information contained in: VAC C-2 Study, Section 1, j; VAC C-2 Special Interrogation Report of Major Hara, Mitsuaki, CO of 1st Bn, 145th Infantry Regiment, 22Mar45, hereinafter cited as Hara: The New York Times, 3Mar45.

21. Major General Osuku, first commanding officer of this organization, was relieved by General Senda in December 1944 when hospitalized on Iwo for paratyphus. Horie, 3.

22. The Brigade Artillery Group also exercised operational control over all naval coast defense guns. CinCPac-CinCPOA Bulletin No 122-45, 1Jun45, 29.

23. LtCol Takeo Nishi, who commanded the 26th Tank Regiment on Iwo, was a champion of "Olympic Horse Games." Horie, 3.

24. Fifth Amphibious Corps Landing Force, Assistant Chief of Staff, G-2, Special Action Report, Iwo Jima Campaign, 20Apr45. Hereinafter cited as VAC IntelRpt. For enemy order of battle see Appendix VI.

25. The preceding information on enemy naval forces and commands was derived from the following sources: CinCPac-CinCPOA Bulletin No 79045, 27Mar45, 56, 79; CinCPac-CinCPOA Bulletin No 124-45, 1Jul45, 32, 37; VAC IntelRpt, 10.

26. VAC IntelRpt, 14.

27. CinCPac-CinCPOA Bulletin No 1490-45, 7Jun45, 81-90.

28. Hara.

29. Japanese Studies; Horie.

30. Ibid.

31. VAC IntelRpt, 16-17.

32. Ibid., 18. A Japanese major captured in Iwo, when asked whether Kuribayashi's tactics might be an indication of a new plan for defense of other strongholds, replied that, ". . . it was a matter of individual temperaments on the part of the various CO's and no conclusions should be drawn relative to operations." Hara. There is evidence to support the conjecture that this difference of opinion between Kuribayashi and his chief of staff became a major point of personal contention. In December Hori was ". . . discharged from this position [Chief of Staff, 109th Division] . . ." and replaced by Col Takaishi.

33. 4th Marine Division, D-2 Language Section Translations, "TAN OpOrder A. No 43, Iwo Jima, 1Dec44," hereinafter cited as TAN OpOrder.

34. CinCPac-CinCPOA Bulletin No 122-45, "Artillery Battle Plan for Iwo Jima," 1Jun45, 30.

35. Ibid., 31.

36. Ibid.

37. CinCPac-CinCPOA Bulletin No 140-45 "Iwo Jima AA Arty Unit Battle Plan," 7Jun45, 71.

38. Weapons information in this paragraph was taken from CinCPac-CinCPOA Bulletin No 152-45, 1Jul45, 38, 76, 80, 84; CinCPac-CinCPOA Bulletin No 6-45, 4th Supplement, 4Jun45; VAC IntelRpt, 18.

39. CinCPac-CinCPOA Bulletin No 152-45, 1Jul45, 76; CinCPac-CinCPOA Bulletin No 161-45, 27Jun45, 126; Expeditionary Troops (TF 56) Report of Intelligence, Iwo Jima Operation, 1Apr45, Encl C, Part III, 38. Hereinafter cited as TF 56 IntelRpt.

40. 3d Marine Division, G-2 Language Section, "Aggregate Report from POW's who worked on Communication Center Pillbox and Tunnels leading thereto from various units," 2Mar45.

41. 4th MarDiv D-2 Language Section, Preliminary POW Report No. 13.

42. Japanese Studies.

43. VAC IntelRpt, Encl H. Although this captured enemy survey sketch bears the notation, "Completed 6 February 1945," it is not known whether these planned defenses reached completion prior to 19Feb45.

44. The foregoing account of Japanese defense construction was derived from the following sources: VAC IntelRpt; Military Intelligence Service, War Department, Washington, D.C., Tactical and Technical Trends, No. 58, May 1945 (U.S. Government Printing Office, 1945), 1-15.

45. CinCPac-CinCPOA Bulletin No 122-45, 1Jun45, "Air Transport at Iwo Jima, Nanpo Shoto Naval Air Group Transport Office August 1944-February 1945, 55-100." Other interesting items mentioned are a shipment of "Imperial Gifts (Sake)", for the Commander of the 27th Air Flotilla and three swords consigned to Rear Admiral Ichimaru.

46. CinCPac-CinCPOA Bulletin No 75-45, 20Mar45, "List of Planes Using Motoyama Airfield #1, between 1 January and 14 February 1945," 108.

47. Contained in Instructions of War telegraphed from LtGen Kuribayashi to Chief of the General Staff, as quoted from memory in Horie.

48. CinCPac-CinCPOA Bulleting No 17045, 7Jul45, "Japanese Criticism of Artillery Maneuvers on Iwo Jima," 27-42.

49. TAN OpOrder.

50. TF 56 IntelRpt, 41.

51. Ibid.

52. 4th MarDiv D-2 Language Section Enemy Diary Translation, 28Feb45. This was actually the D-minus 2 UDT operations described later in this monograph.

53. 4th MarDiv D-2 Language Section Translation, 26Feb45.

54. Ibid.