'Detachment' was the US seizure of Iwo Jima island, the central and largest of the three islands of the Kazan-retto (Volcano islands group) (19 February/26 March 1945).
The importance of this undertaking for the Americans lay in the fact that the island’s capture provided the US forces with two completed airfields and one incomplete airfield. These could then be brought into service for emergency landings by Boeing B-29 Superfortress heavy bombers damaged over Japan and unlikely to make it back to their bases in the Mariana islands (seized by US forces in 'Forager' between 15 June and 10 August 1944) and also as bases for long-range fighters, which could therefore escort the bombers operating against targets in the Japanese home islands from the large bases on the Mariana islands. At the psychological level the operation also signalled to the Japanese the fact that the US forces were still driving forward on Japan and that the island’s loss was a clear sign of inevitable defeat, with only Okinawa left between the advancing Americans and the home islands.
Iwo Jima is one of the Kazan-retto (Volcano islands group), the southernmost part of the Ogasawara-gunto (Bonin islands group), which lies about 670 miles (1080 km) to the south of Tokyo and 625 miles (1130 km) to the north of Saipan, and thus almost exactly half-way between Tokyo and Saipan. On its north-east/south-west long axis, the island measures less than 5 miles (8 km), and its width from about 2.5 miles (4 km) in the northern portion to a mere 0.5 mile (0.8 km) in the southern portion. The island has an area of less than 8 sq miles (20.7 km˛), relies on trapping of rain for its fresh water, and in its simplest terms is a very rugged plateau dominated at its northern end by a mass of low but sharp ridges and ravines, and at its southern tip by Mt Suribachi, the 546-ft (166-m) stump of an extinct volcano and the island’s highest point.
At the time of the Japanese 'Ai' attack on Pearl Harbor in December 1941, an Japanese army force of some 3,700 to 3,800 men garrisoned Chichi Jima, the largest of the Ogasawara-gunto’s islands, and the Japanese navy had some 1,200 men at the Chichi Jima naval base, a small seaplane base, a radio and weather station, and various gunboat, submarine chaser and minesweeper units.
On Iwo Jima, the Japanese navy had constructed an airfield about 2,000 yards (1830 m) to the north-east of Mt Suribachi. Initially stationed on this field were 1,500 Japanese navy air force personnel and 20 aircraft.
In the wake of the US seizure of the Marshall islands group, starting with 'Galvanic' in November 1943, and the devastating 'Hailstone' air offensive against the Japanese naval strength located at Truk atoll in the Caroline islands group during February 1944, the Japanese high command completed a major reassessment of Japan’s strategic situation. It seemed clear that there would be US offensives against the Mariana and Caroline island groups, which were in fact undertaken as 'Forager' and 'Stalemate II' in July and September 1944 respectively. To counter such a move, the Japanese decided to create an inner defence perimeter extending basically to the north from the Caroline islands group to the Mariana islands group, and thence to the Ogasawara-gunto. In March 1944 General Hideyoshi Obata’s 31st Army, headquartered on Truk island, was activated to garrison this inner defence line, and the commander of the Chichi Jima garrison was placed in nominal command of the Japanese army and navy units in the Ogasawara-gunto.
Following the US seizure of bases in the Marshall islands group, in the 'Flintlock' and 'Catchpole' battles for Kwajalein and Eniwetok atolls respectively, during February 1944 the Japanese army and navy each despatched reinforcements to Iwo Jima. Some 500 men from the naval base at Yokosuka and an additional 500 from Chichi Jima arrived during March and April 1944, and at the same time the arrival of reinforcements from the home islands boosted the strength of the Japanese army garrison on Iwo Jima to more than 5,000 men with 13 pieces of artillery and 200 machine guns. The defence also boasted 120-mm (4.72-in) coast defence guns, 12 heavy anti-aircraft guns, and 30 25-mm twin anti-aircraft cannon.
The loss of the Mariana islands group during the summer of 1944 greatly increased the strategic significance of the Ogasawara-gunto and Kazan-retto to the Japanese, who were only too aware that the loss of these islands would enhance the efficacy of US air raids against the home islands as, from bases in the Mariana islands group, the US bomber offensive would be considerably more effective than that that flying from Chinese bases.
The final Japanese plans for the defence of the Ogasawara-gunto and Kazan-retto were overshadowed by the fact that the Japanese navy had already lost most of its strength, especially in the devastatingly unsuccessful 'A' and 'Sho' operations off the Mariana and Philippine island groups respectively, and could therefore no longer be seen as a significant element in any Japanese plan to defeat the inevitable US assault. Moreover, Japanese aircraft losses throughout 1944 had been so heavy that, even without the increasing effect of the US bombing campaign, the overall strength of the Japanese air forces was not expected to increase to 3,000 aircraft until March or April 1945. Even then, these aircraft could not be used from bases in the home islands against US forces based on a captured Iwo Jima because their range did not exceed 550 miles (890 km). Moreover, all available aircraft had to be retained for possible use on Taiwan and other nearby islands off the coast of China, where land bases were available in close proximity to any fighting which might start.
Thus in the battle to hold Iwo Jima the Japanese used only ground units. Even so, the defence of Iwo Jima was based on the knowledge that victory on the island was impossible, and that the island should therefore be held for as long as possible to increase the time available for the preparation of an effective defence of the Japanese home islands, and even kamikaze air attacks, surprise attacks by submarines, and coup-de-main operations by parachute units were seen only within this context.
In the first weeks of 1945, Japan faced the prospect of invasion by Allied forces. On a daily basis 'Scavenger' bomber raids from the Mariana islands group were striking targets in the Japanese home islands, and in the battle to check if not defeat this US offensive Iwo Jima was a vital early warning station from which radio reports of inbound bomber formations could be sent to the home islands, thus facilitating the task of the Japanese army and navy air forces in getting adequate numbers of fighters into the air above the anticipated targets.
At the end of the 'King II' offensive which took Leyte island in the Philippine islands group by the end of December 1944, the Americans had a two-month interval in their operational schedule before the planned 'Iceberg' invasion of Okinawa and, deemed unacceptable, this lull was filled by the 'Detachment' capture of Iwo Jima.
Even before the fall of Saipan in July 1944, Japanese planners knew that Iwo Jima would have to be reinforced materially if it was to be held for any useful length of time, and preparations had then been made to send sizeable personnel and matériel reinforcements to the island. At a time late in May, Lieutenant General Tadamichi Kuribayashi was given the task of holding Iwo Jima, and by 8 June was on his way to convert the island into a fortress which could withstand any type of attack for an extended period. When Kuribayashi reached his new command, some 80 fighter aircraft were stationed on Iwo Jima, but by a time early in July there were just four left.
Then a US Navy task force approached the island and subjected it to a two-day gunfire bombardment, which destroyed every building on the island and smashed the four remaining aircraft. Much to the surprise of the Japanese garrison, a US invasion did not take place during the summer of 1944. Even so, no one had any doubt that in time the Americans would indeed launch an invasion.
As a first step in readying Iwo Jima, Kuribayashi ordered the evacuation of all civilians, and this exodus was completed late in July. Next came an overall plan for defence of the island. Up to the time of his return to the Mariana islands group, Obata had adhered to the well established Japanese tactical doctrine that an amphibious invasion had to be beaten back right on the water’s edge, and had accordingly ordered the emplacement of artillery and the construction of pillboxes dominating Iwo Jima’s beaches. Kuribayashi had different ideas: he felt that any effort to hold the Americans right on the beaches would be futile, and therefore planned to screen the beaches with only modest numbers of automatic weapons and infantry, while his more effective weapons (artillery, mortars and rockets) were emplaced on the foot and slopes of Mt Suribachi, as well as in the high ground to the north of Chidori Airfield No. 1.
Kuribayashi also believed that any prolonged defence of the island had to be based on an extensive system of caves and tunnels, for the naval bombardment had clearly shown that surface installations could not withstand prolonged shelling. To this end, mining engineers were summoned from Japan to plan and construct a complex of underground fortifications based on an elaborate network of tunnels at varying depths to assure good ventilation and minimise the effect of bombs or shells exploding near the entrances or exits of the tunnels.
Over this period the island was gradually being reinforced. As commander of the 109th Division, Kuribayashi decided first of all to shift Major General Kotoo Osuga’s 2nd Independent Mixed Brigade, comprising some 5,000 men (309th to 312th and 314th Independent Battalions, as well as artillery, engineer and communications elements), from Chichi Jima to Iwo Jima. With the fall of Saipan, 2,700 men of Colonel Masuo Ikeda’s 145th Regiment (four battalions) of the same division’s 1st Mixed Brigade, under the command of Major General Yoshio Tachibana, who succeeded Kuribayashi in command of the 109th Division and the island’s defences on the latter’s loss on 23/26 March, were diverted to Iwo Jima. These reinforcements, which reached the island during July and August 1944, raised the strength of the army garrison to about 12,700 men. Next there arrived 1,233 men of the 204th Naval Construction Battalion, which quickly set to work building concrete pillboxes and other fortifications.
On 10 August 1944, Rear Admiral Toshinosuke Ichimaru reached Iwo Jima just before another 2,216 naval personnel including naval aviators and ground crews, who were organised into combat battalions. Next came artillery units and five anti-tank battalions. Even though numerous supply ships were sunk by US aircraft and submarines while trying to reach Iwo Jima, substantial quantities of matériel reached the island during the summer and autumn of 1944.
By the end of the year, therefore, Kuribayashi had available to him 361 pieces of artillery in calibres of 75 mm (2.95 in) or greater, 12 320-mm (12.6-in) mortars, 65 150-mm (5.91-in) heavy and 81-mm (3.2-in) medium mortars, 33 naval guns in calibres of 80 mm (3.15 in) or greater, and 94 anti-aircraft guns in calibres of 75 mm (2.95 in) or greater. In addition to these large-calibre weapons, the defences of Iwo Jima had more than 200 20-mm and 25-mm anti-aircraft cannon as well as 69 37-mm and 47-mm anti-tank guns. The fire power of the artillery was further supplemented by a variety of rockets varying from a 203-mm (8-in) type weighing 198 lb (90 kg) and possessing a range of up to 3000 m (3,280 yards) to a giant 551-lb (250-kg) projectile possessing a range of more than 7000 m (7,655 yards). In total, the defences of Iwo Jima included more than 70 rocket launchers.
As a further strengthening of the defence, Lieutenant Colonel Baron Takeichi Nishi’s 26th Tank Regiment, stationed at Pusan in southern Korea after extended service in Manchukuo, received orders to move to Iwo Jima. Consisting of 600 men and 28 tanks, the regiment sailed from Japan in mid-July on board the transport Nisshu Maru, but as it approached Chichi Jima in a convoy on 18 July 1944, the ship was torpedoed by the US submarine Cobia. Even though only two members of the 26th Tank Regiment were lost, all of the regiment’s tanks went down with the ship. It would be December before these could be replaced, but 22 tanks finally reached Iwo Jima.
Nishi had initially planned to employ his armour as a type of 'mobile fire brigade' for commitment at key spots and times. The rugged terrain precluded such employment, however, so finally the tanks were deployed in static positions: they were either buried whole or stripped of their turrets, which were emplaced in the rocky terrain so skilfully that they were practically invisible from the air or from the ground.
For the remainder of 1944 the construction of Iwo Jima’s fortifications was driven forward as rapidly and extensively as possible. The Japanese quickly learned that the black volcanic ash that existed in abundance all over the island could be converted into concrete of superior quality when mixed with cement. Pillboxes near the beaches north of Mt Suribachi were constructed of reinforced concrete, many of them with walls 4 ft (1.2 m) thick, and at the same time a complex of caves, concrete blockhouses and pillboxes was established. Thus one of the results of the US air attacks and naval bombardment in the early summer of 1944 had been to drive the Japanese so deep underground that eventually their defences became effectively immune to air or naval bombardment. While the Japanese defenders of Peleliu island in the western part of the Caroline islands group, also awaiting a US attack ('Stalemate II'), had turned the improvement of natural caves into an art, those of Iwo Jima developed it into a science.
Because of the importance of the underground positions, 25% of the garrison was detailed to tunnelling. Underground positions ranged in size from small caves for a few men to several underground chambers each capable of holding 300 or 400 men. In order to prevent personnel from becoming trapped in any one excavation, the subterranean installations were provided with multiple entrances and exits, as well as stairways and interconnecting passageways. Special attention was paid to the provision of adequate ventilation, since fumes from the island’s sulphur deposits were present in many of the underground installations. Fortunately for the Japanese, most of the volcanic stone on Iwo Jima was so soft that it could be cut with hand tools.
Kuribayashi established his command post in the northern part of the island, about 550 yards (500 m) to the north-east of Kita village and to the south of Kitano Point. This installation, 65 ft (20 m) underground, consisted of caves of varying sizes connected by 165 yards (150 m) of tunnels.
Farther to the south, on Hill 382, the second highest elevation on the island, the Japanese constructed a radio and weather station. Nearby, on a rise just to the south-east of the station, a huge blockhouse was constructed as the headquarters of Colonel Chosaku Kaido, commanding all of Iwo Jima’s artillery.
Other hills in the northern portion of the island were tunnelled out, and typical of the thoroughness employed in the construction of the subterranean defences was the main communications centre to the south of Kita village, which was so spacious that it contained a chamber 55 yards (50 m) long and 22 yards (20 m) wide. This major structure was similar in construction and thickness of walls and ceilings to Kuribayashi’s command post, and was accessed by a 165-yard (150-m) tunnel 65 ft (20 m) below the ground.
Perhaps the most ambitious construction project to get under way was the creation of an underground passageway designed to link all the major defence positions and installations on the island. As projected, this passageway was to have attained a total length of almost 17 miles (27 km) and, had it been completed, would have linked the formidable underground installations in the northern portion of Iwo Jima with the southern part of the island, where the northern slope of Mt Suribachi alone harboured several thousand yards of tunnels. By the time the forces of the US Marine Corps landed on Iwo Jima, more than 11 miles (18 km) of tunnels had been completed.
A supreme physical and psychological effort was required of the Japanese personnel engaged in the underground construction work. Aside from the heavy physical labour, the men were exposed to heat from 30 to 50° C (85 to 120° F), as well as sulphur fumes that forced them to wear gas masks. In numerous instances a work detail had to be relieved after only five minutes. When renewed US air attacks struck the island on 8 December 1944 and thereafter became a daily occurrence until the invasion started, large numbers of men had to be diverted to repairing the damaged airfields.
As Iwo Jima was being converted into a sturdy fortress with all possible speed, Kuribayashi formulated his final defensive plan. A radical departure from the defensive tactics used by the Japanese earlier in the war, this plan provided for the following major points: in order to prevent disclosing their positions to the Americans, Japanese artillery was to remain silent during the expected pre-landing bombardment, and no fire would be directed against the US Navy vessels; when they landed, the Americans were not to encounter any opposition on the beaches but, after they had advanced some 550 yards (500 m) inland, they were to be taken under the concentrated fire of automatic weapons stationed in the vicinity of Motoyama Airfield No. 2 to the north, as well as automatic weapons and artillery emplaced both on the high ground north of the landing beaches and on Mt Suribachi to the south. After inflicting maximum possible casualties and damage on the landing force, the artillery was to move to the north from the high ground near Chidori Airfield No. 1.
In this connection, Kuribayashi stressed the need for the conduct of an elastic defence designed to wear down and attenuate the invasion force. Such prolonged resistance naturally required the defending force to stockpile rations and ammunition. To this end the island’s commander accumulated a food reserve to last for two and a half months, ever mindful of the fact that the trickle of supplies which was reaching Iwo Jima during the latter part of 1944 would cease altogether once the island was surrounded by the US Navy’s warships and transports.
During the final months of preparing the defences, Kuribayashi saw to it that the building of fortifications did not interfere with the training of units. As an initial step toward obtaining more time for training, he ordered work on the northernmost of the island’s three airfields to be halted. In an operations order issued in early December, Kuribayashi set 11 February 1945 as the target date for completion of defensive preparations and specified that personnel were to spend 70% of their time in training and 30% in construction work.
Despite intermittent harassment by US submarines and aircraft, additional personnel continued to arrive on Iwo Jima until February 1945, by which time Kuribayashi had under his command a force totalling between 21,000 and 23,000 men, including both army and navy units: a reasonable estimate suggests a minimum of 13,585 army troops and 7,345 naval personnel, but the total may have reached 22,060 men.
Kuribayashi made several changes in his basic defence plan in the months preceding the US invasion. The final version, which became effective in January 1945, called for the creation of strong, mutually supporting positions which were to be defended to the death without any thought of large-scale counterattacks, withdrawals or banzai charges. The southern portion of Iwo Jima, near Mt Suribachi, was organised into a semi-independent defence sector whose fortifications included casemated coast artillery and automatic weapons in mutually supporting pillboxes. The narrow isthmus north of Mt Suribachi was defended by only a small infantry force. On the other hand this entire area was exposed to the fire of artillery, rocket launchers and mortars emplaced on Mt Suribachi to the south and the high ground to the north. A primary defence line, consisting of mutually supporting positions in depth, extended from the north-western part of the island to the south-east, along a general line from the cliff in the north-west, across Motoyama Airfield No. 2 to Minami village, and thence eastward to the coast just to the south of Tachiiwa Point. This whole defence line was dotted with pillboxes, bunkers and blockhouses. Nishi’s immobilised tanks, carefully dug in and camouflaged, further strengthened this fortified area, whose defensive capability was enhanced by the broken and very rugged terrain.
A second defence line extended from a position a few hundred yards to the south of Kitano Point at the very northern tip of Iwo Jima across the incomplete Airfield No. 3, to Motoyama village, and thence to the area between Tachiiwa Point and the East Boat Basin. This second line contained fewer man-made fortifications, but the Japanese took maximum advantage of natural caves and other terrain features to enhance the defence.
As further protection for the island’s two completed airfields against direct assault, the Japanese constructed a number of anti-tank ditches near the fields and mined all the natural lines of approach. When, on 2 January, more than a dozen Consolidated B-24 Liberator bombers raided Chidori Airfield No. 1 and inflicted heavy damage, Kuribayashi diverted more than 600 men, 11 trucks, and two bulldozers for immediate repairs. As a result, the airfield was rendered operable once more after only 12 hours. Eventually, 2,000 men were assigned the job of filling the bomb craters, as many as 50 men being detailed to each bomb crater.
The end of 1944 saw B-24 bombers over Iwo Jima almost every night, while US Navy carriers and cruisers frequently sortied into the Ogasawara-gunto and Kazan-retto. On 8 December 1944 US aircraft dropped more than 800 tons of bombs on Iwo Jima, a total which caused very little real damage to the island’s defences. Even though frequent air raids interfered with the Japanese defensive preparations and robbed the garrison of much badly needed sleep, progress on the defensive preparations was not materially slowed.
On 13 February, a Japanese patrol aeroplane spotted 170 US ships steaming to the north-west from Saipan in the Mariana islands group. All Japanese forces in the Ogasawara-gunto and Kazan-retto were alerted and occupied their battle positions. On Iwo Jima, preparations for the pending battle had been completed, and the defenders were ready.
On 7 October 1944 Admiral Chester W. Nimitz and his staff had issued a staff study for preliminary planning of 'Detachment' to maintain constant military pressure against Japan, to extend US control over the western reaches of the Pacific Ocean and, from mid-July 1944 and the capture of Saipan, to provide the USAAF with a forward base. General Henry H. Arnold, commanding the USAAF, urged the paramount importance of acquiring the island’s airfields for offensive purposes, and a defensive need soon became apparent as Japanese bombers staging through the island of Iwo Jima attacked US positions on the Mariana islands group and caused great damage, including the destruction of 15 B-29 bombers and the damaging of more than another 40. Air attacks failed to neutralise Iwo Jima’s airfields and early warning radar, so it became clear that an amphibious assault would be required.
In US hands, Iwo Jima could be turned into a base from which to attack the Japanese home islands, protect bases in the Mariana islands group, cover naval forces, conduct search operations of the approaches to the Japanese home islands, and provide fighter escort for long-range bomber operations. Three tasks specifically envisaged in the study were the reduction of Japanese naval and air strengths and also of industrial capacity in the home islands; the destruction of Japanese naval and air strength in the Bonin islands; and the capture, occupation and subsequent defence of Iwo Jima for development as a major air base.
On 9 October, Lieutenant General Holland M. Smith, commanding the Fleet Marine Force, Pacific, received the staff study, accompanied by a directive from Nimitz ordering the seizure of Iwo Jima. This directive designated specific commanders for the operation. Admiral Raymond A. Spruance, heading the 5th Fleet, was placed in overall command of Task Force 50. Under Spruance, Vice Admiral Richmond K. Turner, commanding the Amphibious Forces, Pacific, was to lead the Joint Expeditionary Force (TF51) and had under his command some 1,300 ships for the movement, landing and support of the invasion force. Second in command of the JEF was Rear Admiral Harry W. Hill. Smith was designated as commander of the Expeditionary Troops (TF56). All of these men had shown their exceptional capabilities in previous campaigns.
TF56 was centred on Major General Harry Schmidt’s V Amphibious Corps, comprising Major General Graves B. Erskine’s 17,715-man 3rd Marine Division (3rd, 9th and 21st Marines plus the 12th Marine Artillery), Major General Clifton B. Cates’s 18,241-man 4th Marine Division (23rd, 24th and 25th Marines plus the 14th Marine Artillery) and Major General Keller E. Rockey’s 18,311-man 5th Marine Division (26th, 27th and 28th Marines plus the 13th Marine Artillery).
Schmidt’s plan for the landings was straightforward: the 4th and 5th Marine Divisions were to land side-by-side on the eastern beaches, the former on the right and the latter on the left, and when released to the V Amphibious Corps, the 3rd Marine Division, as Expeditionary Troops Reserve, was to land over the same beaches to take part in the attack or play a defensive role as demanded by the tactical situation. The plan called for a rapid exploitation of the beach-head with an advance in a north-easterly direction to capture the entire island. One regiment of the 5th Marine Division was assigned to the capture of Mt Suribachi in the south.
Since there was a possibility of unfavourable surf conditions along the eastern beaches, the V Amphibious Corps issued an alternative plan on 8 January 1945 for a landing on the western beaches. However, since the predominant northerly or north-westerly winds caused hazardous swells almost continuously along the south-western side of the island, it appeared unlikely that this alternative plan would be put into execution.
The detailed plan for the landings provided for two battalions of Colonel Harry B. Liversedge’s 28th Marines of the 5th Marine Division to land on the extreme left of the corps on Green 1 beach. On the right of the 28th Marines, Colonel Thomas A. Wornham’s 27th Marines was to land single battalions on Red 1 and Red 2 beaches, and then attack toward the west coast of the island before wheeling to the north for the seizure of the western end of the O-1 Line between the East Boat Basin and the west coast via Motoyama Airfield No. 2. Action by the 27th and 28th Marines was designed to drive the Japanese from the commanding heights along the southern portion of Iwo Jima, simultaneously securing the flanks and rear of the V Amphibious Corps.
As far as the 4th Marine Division was concerned, Colonel Walter W. Wensinger’s 23rd Marines was to land single battalions on Yellow 1 and Yellow 2 beaches, seize Chidori Airfield No. 1, then turn to the north-east and seize that part of Motoyama Airfield No. 2 and the O-1 Line within its zone of action. After landing on Blue 1 beach, two battalions of Colonel John R. Lanigan’s 25th Marines were to assist in the capture of Motoyama Airfield No. 2, the capture of Blue 2 beach just to the south of the East Boat Basin and thus on the extreme right of the V Amphibious Corps, and the O-1 Line within its zone of action.
Colonel Walter I. Jordan’s 24th Marines was to be held in 4th Marine Division reserve during the initial landings. Colonel Chester B. Graham’s 26th Marines was to be released from corps reserve on D-day and be prepared to support the 5th Marine Division.
The divisional artillery was to go ashore on order from the respective division commanders. The 4th Marine Division was to be supported by Colonel Louis G. DeHaven’s 14th Marines, and Colonel James D. Waller’s 13th Marines was to furnish similar support for the 5th Marine Division.
The operation was to start with the simultaneous arrival on the assault beach of the 68 LVTs carrying the first wave of men. These vehicles were to advance inland until they reached the first terrace beyond the high-water mark. The LVTs were to use their 75-mm (2.95-in) howitzers and machine guns to keep the heads of the Japanese down, thus giving some measure of protection to succeeding waves of marines, who would be most vulnerable to Japanese fire as they disembarked from their LVTs. Early versions of the V Amphibious Corps' operations plan had called for tanks of the 4th and 5th Marine Tank Battalions to be landed at H+30, but later consideration of the beaches made it necessary to adopt a more flexible schedule. The possibility of congestion at the water’s edge also contributed to this change in plans. In the end, the time for bringing the tanks ashore was left to the discretion of the regimental commanders.
In the period leading up to 'Detachment', the US forces undertook 'Jamboree' as their first major raid on Tokyo with carrierborne aircraft.
The final preparations for 'Detachment' had meanwhile been completed on 16/19 February. On 16 February Rear Admiral Bertram J. Rodgers’s TF54, comprising the battleships Tennessee, Idaho, Nevada, Texas, New York and Arkansas, the heavy cruisers Chester, Salt Lake City, Pensacola and Tuscaloosa, the light cruiser Vicksburg and 16 destroyers of Destroyer Squadron 51 and Destroyer Divisions 91 and 112, approached Iwo Jima and started a gunfire bombardment of the designated areas in preparation for the assault.
Rear Admiral William H. P. Blandy’s TF52 (Support Force), with the Minesweeper Group 52.3, Frogman Group 52.4 and LCI Support Group 52.5, and Rear Admiral Calvin T. Durgin’s TG52.2 (Escort Carrier Group 52.2 with the escort carriers Sargent Bay, Natoma Bay, Wake Island, Petrof Bay, Steamer Bay, Makin Island, Lunga Point, Bismarck Sea, Saginaw Bay and Rudyerd Bay, with their escort of destroyers and destroyer escorts, provided air cover and flew 158 attack sorties. The effect of the gunfire bombardment was slight because of inadequate observation in poor weather, but a repetition on 17 February in better weather was deemed to be more successful. The Japanese coastal batteries obtained one hit on Tennessee, six on Pensacola and one on the destroyer Leutze.
After disembarkation from the troop-carrying destroyer conversions Bull, Bates, Barr and Blessman, the underwater demolition teams started on the task of removing underwater obstacles. All 12 infantry landing craft used for support were hit by the Japanese coastal batteries, and nine of them were put out of action.
The escort carriers flew off 226 sorties, some with napalm. Forty-two Consolidated B-24 Liberator heavy bombers of Major General Thomas D. White’s 7th AAF also made attacks. On 18 February the shelling and air attacks were continued, the latter totalling only 28 heavy bomber sorties. Including air escorts, the escort carriers' aircraft flew 612 sorties in all and lost three of their number.
The destroyer minesweeper Gamble was damaged beyond repair by a Japanese naval aeroplane during this day, and the high-speed transport destroyer Blessman was damaged.
On the following day, 19 February, the landings on Iwo Jima got under way with Turner’s TF51 delivering and disembarking Schmidt’s V Amphibious Corps. TF51 consisted of 495 ships allocated four task groups (TG52, TG53, TG54 and TG56). On 19 February Rodgers’s TF54, reinforced by the battleships North Carolina and Washington, heavy cruiser Indianapolis, light cruisers Santa Fe and Biloxi, and 10 destroyers from two destroyer divisions of TF58, completed a heavy preliminary gunfire bombardment of the assault areas, this being interspersed with attacks by the carrierborne aircraft of TG58.2 and TG58.3.
The landings were effected by Hill’s TF53: in the north the 4th Marine Division was landed by Commodore H. C. Flanagan’s TG53.2 from 15 attack transports, six attack cargo ships, two landing ship docks, 19 tank landing ships and 12 medium landing ships, and in the south the 5th Marine Division by Commodore J. B. McGovern’s TG53.1 from 15 attack transports, six attack cargo ships, one landing ship dock, 19 tank landing ships and 16 medium landing ships. Each of these two task groups was escorted by one destroyer squadron. Another task group had the 3rd Marine Division on board as a floating reserve, of which part had to be landed on the first day.
On 19 February the Americans put ashore some 30,000 men, and these had the support of the aircraft of the fleet and light carriers of TG58.2 and TG58.3 as well as of the escort carriers of TG52.2. The marines faced determined opposition, and carrierborne aircraft thus flew 606 sorties on the first day, using 274 tons of bombs, 2,254 rockets and more than 100 napalm tanks. Japanese shore batteries damaged the destroyer John W. Weeks and four mechanised landing ships, and damage also resulted from collisions involving the cruiser Chester with the amphibious force flagship Estes, the cruiser Indianapolis with the ammunition ship Shasta, the destroyer escort Finnegan with LCI(L)-627, and the cruiser Salt Lake City with the transport Starr.
On 21 February TG58.1 and TG58.4 provided support for the disembarked forces while TG58.2 and TG58.3 moved farther offshore to replenish. The only Japanese response from anywhere off Iwo Jima was a kamikaze attack by 32 aircraft on 21 February: the escort carrier Bismarck Sea was sunk and the fleet carrier Saratoga, the light carrier Langley and the escort carrier Lunga Point, the transport Keokuk, and LST-477 and LST-809 were damaged. Saratoga sustained severe damage, her casualties totalling 123 dead and 192 wounded, and Bismarck Sea lost 218 men. There were several further collisions, causing damage to destroyers and auxiliaries.
The Japanese submarines Ro-43 and 'Kaiten'-carrying I-368, I-370 and I-44 were deployed as the 'Chihaya' Group, and later I-36 and I-58 were ordered into the area as the 'Kamitake' Group.
The escort carriers Tulagi and Anzio led carrier/destroyer escort groups in the submarine hunter/killer role, and on 25/26 February aircraft from Anzio sank Ro-43 and I-368, and the destroyer escort Finnegan, part of a convoy escort, sank I-370. Ro-43 managed to attack an escort, torpedoing the destroyer Renshaw on 21 February.
As noted above, on 16 February the US forces had begun a massive three-day air and naval bombardment of Iwo Jima. The second day of bombardment was so furious that the Japanese thought the invasion was imminent and many of the gunners forgot Kuribayashi’s orders to hold their fire. The Japanese thus opened a furious fire on the closer US warships and the specialised landing craft undertaking tasks such as the bombardment of the shoreline with rockets and the delivery of frogmen for underwater reconnaissance of the beaches and their approaches. The cruiser Pensacola was hit by six shells which killed 17 men and wounded more than 100 others, a destroyer took a direct hit which killed seven men and wounded another 33, and the landing craft suffered badly. The US ships pulled back under cover of a smokescreen, and the Japanese concluded that they had beaten off an invasion attempt.
The Americans now realised that the earlier bombings and the first two days of the naval bombardment had not been as effective as anticipated, and also that many artillery positions had not yet been pinpointed. The third day of the air and naval barrage therefore saw the bombardment force, including five old battleships, close to within 1.5 miles (2.4 km) of the beach to attempt the destruction of all the defensive positions threatening the next day’s assault area: many of these positions were destroyed, but many others survived as poor weather prevented accurate aerial spotting.
After a 72-day aerial bombardment (mostly by B-24 Liberator bombers occasionally supplemented by B-29 Superfortress bombers) and a three-day naval bombardment, D-day was signalled at 02.00 on 19 February by warship guns in a 30-minute barrage that saw the delivery of more than 8,000 shells ranging in calibre from 5 to 16 in (127 to 406 mm). Soon 100 bombers attacked the island, followed by another barrage from the naval guns.
At 08.29, the first of an eventual 30,000 marines of the 3rd, 4th, and 5th Marine Divisions landed and 'Detachment' had truly started.
The first of four assault waves reached the assault beaches in LVTs and landing craft, the troops immediately running into problems as they tried to scale the soft embankment behind the beach while still carrying their heavy equipment packs; at first it seemed that this would be the marines' only difficulty, for they were greeted only by sporadic fire. After 20 minutes, however, the Japanese recovered from the daze into which they had been stunned by the 30-minute naval bombardment and opened fire with every weapon that would bear on the men of the four infantry regiments landed by the 4th and 5th Marine Divisions. The assault forces were soon pinned on their beaches, and this greatly increased the problems faced by the landing craft bringing in the assault divisions' two artillery regiments and the bulldozers tasked with creating the beach exits needed by the tanks that would now be the only way for the US forces to break out of their very shallow beach-head. Some units did achieve this feat, and by the end of 19 February elements of the 5th Marine Division had managed to advance right across the island at its narrowest point just to the north of Mt Suribachi.
Almost 30,000 US Marines were landed on the first day, and of these some 2,500 were killed or wounded. On 20 February the US position across the island’s neck and on the south-western shore was consolidated, the US Marines started to fight their way into the defences on the northern side of Mt Suribachi, and the advance to the north began but soon stalled in the face of a Japanese defence that was, as always, extraordinary determined, but in this particular instance also very effective. At the end of the day it was decided that the 3rd Marine Division should also be committed. Men of the 28th Marines completed their encirclement of Mt Suribachi on 21 February, and began their assault up the northern slope on the following day. The first men reached the edge of the crater at the top on 23 February, but it was another six days before this southern pocket of Japanese resistance could be declared secure.
Meanwhile the 23rd and 25th Marines of the 4th Marine Division and the 27th Marines of the 5th Marine Division were battling their way to the north over very difficult terrain and against fanatical resistance, both of which caused a stream of casualties. On 22 February Schmidt ordered the replacement of the hard-hit 25th Marines, on the right wing of the 4th Marine Division, by the 3rd Marine Division’s fresh 21st Marines, but in fact this unit relieved the 23rd Marines on the boundary between the 4th and 5th Marine Divisions. At much the same time Rockey replaced the exhausted 27th Marines with the 26th Marines, and this fresh strength allowed the Americans to push forward over a distance of between 200 and 1,000 yards (180 and 915 m) during the day.
The marines' next objective was Motoyama Airfield No. 2, and the assault for this important tactical objective began on 24 February after an air attack, a 75-minute naval bombardment and a barrage from the marines' own artillery. As a result largely of armoured support, the marines advanced some 500 yards (460 m) before being checked by the Japanese anti-tank guns and minefields on the southern side of the airfield. Schmidt decided to commit the 3rd Marine Division’s last unit, the 9th Marines, in an effort to maintain the momentum of the US advance. During the morning of 25 February, the 9th Marines attacked through the depleted 21st Marines, and there followed three days of bloody combat before the 9th Marines had taken all of Motoyama Airfield No. 2 and the hills just to its north. The somewhat rested 21st Marines then returned to the fray in place of the 9th Marines, and pushed the edge of the US progress through the village of Motoyama to the high ground just to the south of the incomplete Airfield No. 3.
The fighting was bitter in the extreme, and as the Japanese made effective and full use of the area’s caves, which were all but impervious to artillery fire, the marines found that their most effective weapons were the flamethrower and satchel charge. The former either killed the Japanese defenders or drove them underground, whereupon satchel charges could be placed to seal the entrance of any cave.
As the 3rd Marine Division was pressing forward from Motoyama Airfield No. 2 to Airfield No. 3, the 4th and 5th Marine Divisions were also driving slowly forward to take Hill 362A and Hill 382 respectively. Neither could be bypassed, and the marines suffered very heavy casualties in taking both hills: Hill 362A fell to the 28th Marines, which suffered 224 casualties, and in two days of dire fighting that ended on 1 March the regiment cleared the hill and reached the ridge to its north. Hill 362A was an isolated defensive feature, but Hill 382 was just the core of a defensive complex that included an outer line of dug-in tanks and bunkers for artillery and anti-tank guns, and then the defences proper on Hill 382, the ridges and ravines of Turkey Nob, and the large depression of the Amphitheater, all three features soon becoming known as the Meat Grinder.
The battle for the Meat Grinder lasted two weeks and was extremely costly in lives on both sides, though ultimately it was the Japanese who suffered the heavier casualties as the Americans gained the ascendancy. As the 4th Marine Division fought the Meat Grinder battle, the 3rd and 5th Marine Divisions were pressing forward. The 3rd Marine Division captured Hill 362C in a surprise night attack which caught the Japanese completely unaware on 7 March, even though it was mid-afternoon before the whole feature had been taken, and the 5th Marine Division took Hill 362B.
The Americans had now broken through Kuribayashi’s semi-circle of interlocking defensive features extending from Hill 362A, Hill 362B and Hill 362C to the Meat Grinder, and also severed all communication between Kuribayashi and his soldiers. In these circumstances some of the Japanese soldiers attempted a suicide charge against the 4th Marine Division during the night of 8 March. The eventuality that Kuribayashi had feared now came to pass, and by mid-morning on 9 March the Japanese had suffered 650 dead as they tried to break though the junction between the 23rd and 24th Marines. Followed by the capture of the Meat Grinder on the following day, this signalled the end of organised Japanese resistance on Iwo Jima.
It did not signal the end of unorganised resistance, however, for the surviving Japanese were still determined to sell their lives as expensively as possible in three strongpoints, one in front of each marine division. In front of the 3rd Marine Division, to the south-west of Hill 362C, was Cushman’s Pocket named for Lieutenant Colonel Robert E. Cushman, commander of the 2/9th Marines. It required the efforts of three marine battalions before this 450-man pocket was eliminated on 15 March when the last 60 men attempted a suicide change. In front of the 4th Marine Division was a comparable tangle of Japanese holding caves and pillboxes in the ravines extending from the northern plateau to the island’s east coast. The men of the 4th Marine Division attacked on 12 March, and finally reduced the Japanese pocket in four days of fighting. In front of the 5th Marine Division was the Bloody Gorge pocket near Kitano Point on the island’s north-western tip. The 5th Marine Division attacked on 11 March, and by 25 March had eliminated this last vestige of Japanese resistance.
The battle for Iwo Jima was finally over, the Japanese having lost all but 216 of their 22,000-man garrison and the US Marine Corps having suffered just under 25,000 casualties (6,891 men killed and 18,070 wounded). There were also losses among the US Navy personnel involved in 'Detachment', for as noted above on 21 February the Japanese had launched a kamikaze mission against the warships supporting the land fighting with their carrierborne warplanes: of the 50 aircraft despatched by the Japanese, three hit the fleet carrier Saratoga causing considerable damage, including 42 aircraft, and inflicting 315 casualties (123 dead and 192 wounded), one hit the escort carrier Lunga Point causing only modest damage, and two hit the escort carrier Bismarck Sea causing fatal damage and another 300 or so casualties. Other kamikaze aircraft sank an LST and the auxiliary vessel Keokuk.
Yet the value of the island in US hands was amply proved as early as 4 March, while the fighting was still raging, for on this day the first B-29 landed on Chidori Airfield No. 1 as it ran short of fuel while returning from Japan with a weapons bay door jammed open. Eventually 2,251 B-29 bombers, carrying more than 24,500 aircrew, made emergency landings on Iwo Jima.