From: Commander Amphibious Group One (Commander Amphibious Support Force)
Chapter II. Naval Gunfire
This operation clearly demonstrated that previous high altitude bombings and long range bombardment of Iwo Jima directed only into "target areas" achieved negligible damage to the very numerous defenses of the island, which were stout, comparatively small, and well dispersed. Photographic interpretation shows, on the contrary, that the defenses were substantially increased in number during December, January, and early February. The bombardment by this force on 16 and 17 February also had less than the desired effect, due to interference by weather, to the need for giving way to minesweeping and UDT operations, and by lack of thorough familiarity with the actual important targets, and distinguished from a mark on a map, or a photograph. It was not until after fire support ships, their spotting planes, and the support aircraft had worked at the objective for 2 days, had become familiar with the location and appearance of the defenses, and had accurately attacked them with close range gunfire and low altitude air strikes, that substantial results were achieved. This experience emphasizes once again the need for ample time as well as ample ships, aircraft, and ammunition for preliminary reduction of defenses of a strongly defended position. At the same time it is realized that certain defenses will never be destroyed or even discovered until after the troops land.
From: Commanding General, Expeditionary Troops (Commander Task Force 56)
On 8 November, after a more careful study of the target area had been made, V Amphibious Corps submitted a recommendation for a total of 9 days of preliminary bombardment. On 26 November, the Commander, Amphibious forces, United States Pacific fleet, replied to the recommendation with a study indicating the necessity of slightly more than 3 days of bombardment, and a statement that the troops would be provided with the best possible preliminary bombardment consistent with limitations of ammunition supply and time, and the subsequent troop requirements.
On 24 November, V Amphibious Corps requested that 1 additional day of preliminary bombardments be provided. This letter was forwarded with favorable endorsement by the Commanding General, Expeditionary Troops, Fifth Fleet. The Commander, Amphibious Forces, United States Pacific Fleet, forwarded this request, requesting approval provided that there was no objection on the part of the Commander, Fifth Fleet, based on the general strategical situation.
From: Commanding General, Fourth Marine Division, Fleet Marine Force
The Division's concept of NGF requirements for the Iwo Jima operation, which was submitted to VAC LANFOR early in the planning phase, emphasized the necessity for adequate preliminary bombardment of the objective and requested that a minimum of 10 days destructive fire be conducted prior to the landing. It was apparent that in order to insure success of the landing, weapon emplacements, pillboxes, and blockhouses, particularly those located on the right flank of the division zone of action would have to be reduced prior to D-Day by slow, deliberate, destructive fire from ships firing at close ranges. It is considered that the 3 days allowed for the preliminary bombardment was insufficient.
From: Commander Amphibious Group One (Commander Amphibious Support Force)
Each heavy ship was assigned an area of responsibility, all of which taken together, covered the entire island. Bombardment by destroyers for purposes of destruction was not planned, nor was secondary battery fire from heavy ships contemplated, except for counterbattery and UDT cover. The plan provided on D-minus-3 for bombardment at long and medium ranges, not less than 6,000 yards offshore. For this day firing periods were arranged with the view toward having a minimum number of ships firing at one
time and with the intent of having each ship fire for about 6 hours. For D-minus-2 the plan provided for heavy, close range destructive bombardment of the defenses from Suribachi to Higashi from the eastward until about 1030. During this period ships assigned to the western areas were to conduct bombardment from longer ranges necessitated by safety requirements during the close bombardment from the east. At about 1030 major caliber fire from the ships working from Suribachi to the East Boat basin was to stop as the ships withdrew sufficiently to permit ships engaging in support of the UDT's reconnaissance to take station.; From this time until about 1230 the heavy ships on the east, as well as the close supporting destroyers, were to be primarily concerned with the support of UDT's. Upon completion of the UDT operation in the eastern beaches the ships assigned to the western areas from Suribachi to Hiraiwa Bay were to close and commence heavy short-range bombardment while the ships assigned to the eastern beaches were to withdraw to positions clear of this fire and continue their own bombardment at longer ranges. The heavy bombardment from the west was to continue until 1430, at which time the heavy ships were to have withdrawn, permitting vessels engaged in the western UDT reconnaissance to take their stations. From about this time until the completion of the UDT operation the western bombardment was to be largely limited to 5-inch fire in support of these operations. Fires in the sectors to the northward were scheduled to allow each ship therein about 6 hours firing time. Safety considerations, both with regard to minesweeping and ricochets did not permit scheduling these vessels to approach very close to their targets. The schedule for D-minus-1 day contemplated a repetition of the D-minus-2 schedule if further UDT operations (demolitions) were to take place and an extension of the close range firing periods if such operations were not to be carried out.
The plan required deliberate destructive fire at specific individual targets, and the assigned target priorities emphasized fire on defenses and installations which could most severely threaten our ships, our aircraft, and ship-to-shore movement, the landing, and operations immediately following the landing. The total number of defense installations was too great to attempt more than this in view of the limited time and ammunition available before D-day. Great emphasis on the priority principles was made not only in the plan but during the briefing, with the design of concentrating destructive fire on pillboxes, blockhouses, covered gun emplacements, etc., in the landing areas and around Suribachi and on the high ground immediately to the northward of the landing areas. Ships were specifically directed not to expend their efforts on destruction of installations in the northern parts of the island which would not threaten ships or aircraft, the landing or the early stages of subsequent operations: For example, pillboxes on the northern slopes. The fire of the ships having areas from No. 2 airfield and to the northward was directed largely at coastal defense and antiaircraft guns. Continually, in briefing and during the operation, stress was laid on the importance of closing to short ranges to obtain maximum observation and destruction of pin-point targets and familiarization with the areas, ships assigned to the beach areas were provided with large low oblique photographs covering their particular areas.
From: Commander Amphibious Forces, United States Pacific Fleet (Commander Joint Expeditionary Force)
The following new or special features were incorporated in basic plans.
AMPHIBIOUS SUPPORT FORCE
For the first time, at Iwo Jima, all pre-D-day operations were coordinated by an Amphibious Group Commander embarked in an AGC. Thus provided with an adequate staff and all required facilities, Commander Support Force was able to make the preliminary bombardment as efficient as possible. A most important function in this respect is that of continuing target intelligence based on target destruction and new targets discovered. This in turn depends upon continuous evaluation of visual reports and photo interpretation, facilities for which were not available prior to D-day in previous assaults. On D-minus-3 and D-minus-2, destruction of Iwo defenses was disappointing due to the long range incident to waiting for minesweeping. But on D-minus-1 excellent results were obtained. Probably
a majority of the heavy installations commanding the landing beaches were put out of acton prior to H-hour, and little gunfire from fixed guns was experienced.
Three days were allotted to pre-Dog-Day bombardment in order to ensure the destruction of the maximum number of installations and coverage of known positions on the whole island. Sufficient flexibility was allowed in the schedules of fires on these days so that positions stripped of camouflage by heavy caliber fire and discovered by air spot or photographic intelligence could be destroyed, or at least neutralized.
During the pre-Dog-Day bombardment, the intelligence officer of the Amphibious Support Force coordinated all target information. A card was prepared in the following form.
Targets were given a numerical listing (in addition to the location on the air and gunnery target map) and a complete initial list of targets was supplied to each ship in advance of the operation. Additions, deletions and reports were then made by reference to the basic list with a consequent economy of radio transmissions. Targets were assigned to air or naval gunfire as appropriate, and notations and evaluations were based on the report of the ship, plane, air observer or from photo intelligence. On the morning of D-day, the completed target records were delivered to Commander Expeditionary Force, and a transcript to ComLanFor, thereby providing each of them with an up-to-date collection of target information on which to base subsequent deep supporting fires.
Scheduled fires after H-hour were planned to continue for 4 hours and to advance just ahead of the expected line of troop progress. In general, this plan was successful but the troops did not advance as rapidly as the barrage schedule. This required continuous modification of the schedule resulting in repeating fires in certain blocks and delaying the lifting of fires from others.
Shore fire control communications were arranged generally on the same basis as that which worked so successfully in past operations.
As in the past, one frequency was designated "Naval Gunfire Control Net" and used for all gunfire support requests and administrative traffic relative to naval gunfire, except as noted below.
An innovation was the designation of a frequency as the "Naval Gunfire Overload Circuit." This frequency was guarded by the OTC continually so that any ship or shore party concerned with naval gunfire could clear traffic to the OTC when the Gunfire Control Net was crowded. Routine matters such as ammunition reports and reports of firing by ships were handled on the Overload, and this left the main Control Net clear for more important matters.
Another innovation was the "Gunboat Control Net," a separate frequency to handle assignments, reports, and administrative traffic relative to LCI gunboat types, through their task group and unit commanders.
Control of VOF flights was maintained by the Air Spot Control Net (VHF) which was used to handle all administrative matters between the spotting planes and the Naval Gunfire Control Officer. Spotting was done on the regular frequencies and is discussed in greater detail below.
Initial call fire assignments and frequencies were assigned in the Schedule of Fires and were to become effective immediately upon the landing of the Shore Fire Control Parties.
In order to facilitate radio transmissions and prevent error in ammunition reports, a special list of code names was used for all types of ship ammunition including rockets and mortars.
For the close support of the landing, Fire Support Ships were assigned positions between and on the flanks of the landing waves and fire was scheduled as mentioned above. All ships were to maintain at least steerageway except those in the boat lanes while boats were passing. The latter were instructed to clear the boat lanes as soon after How-Hour as it was safe to do so. This fire was to be supplemented by 9 LCI(L)(3)(R)-RCM)'s, and 18 LCI(M)'s from designated positions, and 12 LCI(G)'s and 12 LCS(L)'s which were to precede the leading wave. Twelve LCI(M)'s were available on call in reserve if needed.
LCI(M) MORTAR PLAN
The rapid rate of fire, high trajectory and long range of the 4".2 chemical mortar were considered to have considerable value for beach preparation fire and for deep support subsequent to How-Hour. Consequently, as recommended following the Marianas operation, an effort was made to
develop a craft mounting this weapon and capable of proceeding to the objective under its own power.
Three 4".2 chemical mortars were mounted on an LCI and experiments successfully covered all phases of loading and firing. Additional conversions were made, further tests conducted and standard plans drawn up for delivery of mortar fire from designated positions on the flanks of the beaches and after How-Hour deep support, behind the beaches.
AIR SPOT PLAN
VOF planes of VOC-1, a specially trained observation squadron flying CVE-based fighter planes, were available for spotting purposes. These were to be used primarily with destroyers but were available to spot for larger ships if weather prevented use of float planes or if VO of VCS planes were not available.
Because of the high speed at which VOF aircraft travel, it was necessary for the spotter to control the time of firing so that he would be in a position to observe the fall of shot. This did not prove to be a serious handicap and there was no evidence that effectiveness or volume of fire suffered.
VOF planes had a primary and secondary spotting frequency upon which they could transmit and were unable to shift to any HF frequencies other than those two while airborne. A split phone watch was maintained so that a VHF frequency could be guarded simultaneously (Air Spot Control, SAD, FD, etc.).
Call fire assignments and communications in general functioned excellently though a bit more complicated than in the past by the addition of VOF spotting planes. The Shore Fire Control Party and air spot supplemented each other on the spotting frequency to achieve better results with the firing ship. In most instances where the plane's transmitter was off frequency, the Shore Fire Control Party and Fire Support Ship tuned their receivers as necessary to receive good signals. In a few cases, ships came up on VHF Air Spot Control Net to facilitate establishing communications on the spotting frequency.
For the first few days, regiments submitted requests for fire support directly to CTF 52 with resultant confusion and failure to utilize ships to the best advantage. Later it was possible to set up a system whereby divisions submitted requests to the Naval Gunfire Officer attached to Headquarters Landing Force afloat (and later ashore). Based on information previously given him concerning the number and type of ships available, one consolidated request was then submitted to CTF 52. Requests for day assignments were usually submitted prior to 1500 and for night assignments prior to 0400 in order to allow sufficient time to effect any changes or reliefs necessary.
Assignments were addressed by CTF 52 to the ship involved, Landing Force Naval Gunfire Officer, Division Liaison Officer and regimental Liaison Officer who notified the Battalion Liaison Officer and shore fire control spotter. Frequency to be used, VOF call (if any) and sector from which fire was to be delivered were also designated in the assignment. CTF's 52 and 53 periodically checked the spotting frequencies to see that conditions were satisfactory and, if necessary, assisted in establishing communications.
A large resupply of star shells was provided at the objective since it was anticipated that the demand would be great because of the many caves and irregular terrain which offered excellent opportunities for infiltration during the night. Expectations were fulfilled, for during the period Dog-plus-One through Dog-plus-Eight an average of over 1,000 star shells per night was used.
It is felt that much illumination is still being delivered unnecessarily because of lack of coordination between adjoining battalions in the call for star shells and the desire to maintain constant illumination throughout the night. The best judges of this, however, are division of higher commands ashore.
Notable by its absence was the complaint that empty star shell cases were falling within our own lines. This can be attributed directly to more careful control of line of fire due to greater familiarity on the part of the spotters with star shells and their characteristics.
The LCS(L)(3)'s and LCI(M)'s supported the landing by fire on the beach, behind the beach and on the flanks before and after H-hour. Some were under control of Shore Fire Control Parties
after H-hour. The greater part of enemy fire came from the flanks. The 40-mm. fire of the LCI's at caves and cliff areas on the flanks was effective in reducing enemy machine gun fire on the beaches, while rockets and mortar shells helped to keep down short range enemy mortar fire.
LCI(M)'s were very useful for delivering all-night harassing fire. Initially, three divisions were used nightly, gradually tapering off to one or part of one division. These LCI(M)'s usually came under fire from enemy coast guns and intermediate automatic weapon fire intermittently during the night, and it was necessary to detail a cruiser or destroyer to cover each division. None was hit but there were many near misses.
The LCI(L)(3)(R)(RCM)'s were used for harassing and interdiction fires but their rockets were soon exhausted. As there were no replacements available, the LCI(R)'s were used thereafter for RCM and anti-small-craft patrol duties and smoke craft. The rockets have the advantage of long range (4,000-5,250 yards maximum) but their uncertain flight makes the troops unwilling to have them fired over men or boats or very close to front lines.
LCS's were much used to shoot into the ravines which ran down to the coast. This was done at short range and under control of a Shore Fire Control Party or embarked troop officer. Experience shows, however, that the LCS can distinguish the position of our troops and the general situation ashore near the coast better than anyone ashore not in the front lines. Gradually the troops allowed them more and more initiative as their value became apparent. They should, however, always be under control of a Shore Fire Control Party for safety.
From: Commander Amphibious Group Two (CTF 53 and CTG 51.21)
4".5 rocket fire for beach preparation and close support of the landing was scheduled for delivery by the Gunboat Support Group consisting of two six-ship LCI(G) units and two six-ship LCS(L) units. The plan provided for initial rocket salvos to be delivered by these ships during the period How-minus-Ninety to How-minus-Forty-five for the purpose of detonating possible beach inflammables well in advance of the time troops would land. The plan also provided for two full rocket salvos to be delivered in close support of the leading wave. The first of these was to be delivered on the beach at How-minus-Ten-minutes after which launchers were to be reloaded and the second salvo fired 300 to 500 yards inland from the beach. Strafing by aircraft, scheduled to commence at How-minus-five-minutes, required the second 4".5 rocket salvo to be fired prior to this time.
To prevent early blanketing of supporting fire of two destroyers and a battleship stationed in the boat lanes, the plan prescribed that the four six-ship gunboat units proceed toward shore in unit columns ahead of the leading LVT assault wave. After passing the battleship-destroyer line, the gunboat units were to deploy into line for firing rockets.
Of the original 12 LCI(G)'s of Gunboat Support Units No. 1 and No. 2, only 3 were in condition to deliver the scheduled support on Dog-Day, the other having been lost or damaged by enemy fire on previous days. Units No. 3 and No. 4 consisting of 6 LCS(L)'s each were directed to in crease their spacing on final deployment in order to cover the portions of the beach assigned by plan to the absent LCI(G)'s.
On completion of their rocket salvos at How-minus-Five-minutes, four LCS(L)'s of each of the two gunboat support units took position according to plan, opposite the flanks of the landing area and supported, with 40-mm. fire, battalions to which initially assigned. This fire was directed on the slopes of Suribachi Yama and the high flanking ground on the right of the beach. Until communications were established with assigned spotters previously embarked in one LCS(L) of each unit for this purpose.
Mortar Support Units No. 1, No. 2, and No. 5, consisting of six mortar LCI's, were assigned to provide scheduled flanking and deep supporting mortar fire as follows: Units No. 2 and No. 5, using plan "A," fired from How-minus-Thirty-five to How-minus-Seven-minutes on the eastern slopes and approaches to Suribachi Yama while Unit No. 1, using the same fire delivery plan, delivered fire on the eastern flank high ground during the same period. At How-Hour Units No. 2 and No. 5 in column, entered and crossed the boat lanes from the west, turned shoreward into line and followed the Sixth assault wave toward shore.
At about How-plus-Twenty-minutes, when 2,000 yards from shore all ships of these two units opened fire using plan B with mortar range set for 3,200 yards and swept a rectangular area 2,200 yards long by 1,000 yards deep as they moved in. Stopping and lying to 1,000 yards from shore, fire was then maintained 1,800 yards inland and parallel to the beach until How-plus-Sixty-minutes. At How-minus-Seven, Mortar Support Unit No. 1 shifted its line of fire farther to the east for safety to troops and resumed fire at How-plus-Ten-minutes firing at a reduced rate for neutralization until 1,300; 17,400 rounds of 4".2 mortar were scheduled for delivery in support of the landing by these three units.
RCM and Rocket Support Unit No. 1 consisting of nine 5".0 SSR Rocket LCI's, delivered scheduled neutralization fire on the Motoyama area from 0645 to 1300. All rockets on board these ships (a total of approximately 9,500) were delivered during this period, using standard plan RA from a reference point to northeast of the island. On completion of this fire, all fire support duties of this unit terminated for the remainder of the operation.
The eight LCS(L)'s assigned to flank battalions continued their close fire support missions throughout the day, replacement 40-mm. ammunition being obtained for them from heavy cruisers. For night support, four LCS(L)'s of Unit No. 3 were assigned to support battalions designated by Division Headquarters.
On completion of their scheduled fire, Mortar Support Units NO. 1, No. 2, and No. 5 replenished mortar ammunition and joined Units No. 3 and No. 4 in area Roger awaiting assignment. Night harassing mortar fire requests from Headquarters Landing Force were fulfilled by assignment of Units No. 2 and No. 5 to cover prescribed areas throughout the night using standard plan A and varying the line of fire between specified limits. A total of 24,000 rounds of which 20 percent was WP, were delivered by these two units from reference points 1,000 yards off the northwest and southeast coasts of the island. Large caliber enemy counter fire was received by the northern unit, but was not intense or accurate enough to require the withdrawal of this unit.
LCS(L)'s of Unit No. 4 and LCI(G)'s available from RCM Unit No. 2 were assigned daily to support battalions designated by Headquarters Landing Force. Division intelligence officers, specially trained observers, and naval gunfire liaison officers were frequently embarked in ships for reconnaissance and specific fire missions along the shore lines in advance of troop movement. On March 98 all LCS(L)'s departed the area. On March 12, in anticipation of possible attempt by the enemy to effect evacuation of high ranking Japanese by submarine, an LCI(G) was ordered to patrol the coast line beyond our lines to observe for and prevent any such attempt. This patrol was continued nightly thereafter until the island was secure.
One Mortar Unit continued to be assigned each night to deliver harassing fire. Enemy counter fire continued to require the assignment of a destroyer or cruiser to provide support for the harassing unit. On departure of Units No. 1, No. 2 and No. 5 from the area on February 26, Units No. 3 and No. 4 were reorganized into five-ship divisions. Due to the reduced size of the remaining units and their inexperience in plan A fire delivery, night harassing fires were hereafter delivered using plan C. On 28 February, two more mortar LCI's departed the area, leaving two four-ship units available for mortar fire. On 27 February and for several days thereafter individual mortar LCI's were assigned during daylight to provide direct support to battalions designated by Headquarters Landing Force.
The remaining area into which night harassing fire could safely be delivered, required the employment of only one mortar LCI on the night of 1 March. Thereafter harassing fires at night by these ships was discontinued. On 3 March all remaining mortar LCI's departed the area.
Ammunition expenditures by LCI types exclusive of pre-Dog-Day expenditures, were as follows:
4".2 mortar 60,000 4".5 BR rockets 8,000 40-mm. 116,000 5".0 SSR rockets 9,500
GUNBOATS (LCI(G)'s AND LCS(L)(3)'s)
Heretofore in Central Pacific operations the ship-to-shore movement support by LCI gunboats has consisted of one full rocket salvo delivered on the beach at about How-minus-Ten minutes. At Iwo Jima the gunboat group made an early run toward shore between How-minus-Ninety and
How-minus-Forty-five and delivered initial rocket salvos in an attempt to detonate possible inflammables on the beach well in advance of the time of landing. Another innovation at Iwo Jima was the loading and firing of a second rocket salvo during the ship-to-shore movement of the leading wave. The gunboats fired their first salvo at How-minus-Ten minutes as in past operations, then reloaded rocket racks as they moved in to a range of 600-700 yards from the beach and fired a second salvo at How-minus-Five minutes placing this salvo 300 to 500 yards inland. Since 4".5 rocket fire is more neutralizing than destructive and since its short range prevents its use for neutralization of inland areas, its use has rarely been requested after a landing. The best employment of 4".5 rockets therefore is beach neutralization just prior to the landing and their employment for initial and additional salvos at Iwo Jima is recommended for future landing support.
Prearranged fire schedules provided for the initial assignment of one gunboat unit to support each of the two flank battalions on the beach. Replacement naval gunfire liaison officers and spotters were embarked in the gunboat unit flagship to direct the fire until communications were established with the spotter ashore. This plan provided an excellent neutralizing fire on the flanks of the landing beach and was found to be so effective that the Landing Force requested continuous assignment of one or more gunboats to the battalion on the flanks of the front line for the remainder of the operation.
This was the first operation in which LCI's mounting mortars have been employed by the Fifth Amphibious Force. Their primary mission, as conceived in the initial planning, was the delivery of heavy harassing fire at night to prevent the initiation of organized counterattacks. Their support with this fire was most gratifying and materially reduced the demands for harassing fire by destroyers and cruisers.
Two methods of delivering harassing mortar fire at night were employed at Iwo Jima: (1) Plan A of the standard mortar fire plans, in which five LCI's steam on an eliptical track around an LCI acting as reference ship. Ships fire singly in succession during the two minutes' run on the leg on which they are pointed toward the target area. (2) Plan C in which the six LCI's of a division lie to on a line, 200 yards between ships, and fire when the ship's head is between prescribed limiting lines of fire. Both plans have many advantages and disadvantages. Since it is next to impossible to hold an LCI on an accurate heading for a long period when dead in the water, plan C is unsuitable for interdiction fire where continuous and fairly accurate fire along a definite line is required. Harassing fire, which requires irregular volume and rate of fire with an unsystematic pattern and coverage of the area harassed, is especially typical of the fire to be expected of six LCI's dead in the water all on different headings between prescribed limits. Plan A, on the other hand, has all the fire delivery characteristics most suited for interdiction fire and least suited for harassing fire.
The 3,200-yard range limit of LCI mortar fire requires these ships to approach as close to shore as safe navigation permits in order to place their fire as far inland as possible. On a well defended island such as Iwo Jima, this close approach to shore drew considerable enemy fire even at night. LCI mortar ships found good use for their bow 40-mm. in delivery of counterbattery fire in self-protection, but this was found insufficient and it became necessary to assign one of the general support destroyers or cruisers to cover the nightly harassing mortar LCI unit. In making plans for delivery of night (or day) harassing fire by mortar LCI's, the plans should incorporate the employment of a destroyer, for counter-battery protection of the harassing unit. This ship should work with the Mortar Unit Commander on a common frequency.
On request, individual mortar LCI's were assigned to battalions for direct support, generally to those battalions whose flanks were along the shoreline as in the case of gunboat support. Preliminary reports indicate that this support was more in the form of harassing or neutralization fire for the battalion supported. In rough water, the accuracy of LCI mortar fire in deflection is greatly decreased by rolling and cannot be safely called for in areas close to own troops. LCI mortar fire for direct support should therefore only be expected to accomplish harassing or preparation neutralizing fire for an advance into areas within range of the LCI Mounted mortar.
While the accuracy in deflection of mortar fire from LCI's is greatly affected by rolling and variations in ship head, its accuracy in range is quite dependable and relatively unaffected by motion of the ship. It is therefore very suitable for neutralizing fire over the heads of troops when the line of fire is perpendicular to the line of troops. Its high trajectory makes it ideal for use when ships and troops located between the target and firing ships preclude the use of high velocity flat trajectory fire. At Iwo Jima, the neutralization of large areas inland from the beaches was effectively delivered by mortar fire from LCI's on a line parallel to and 1,000 yards from shore. This fire was not provided however, until How-plus-Twenty minutes. Using Plan B with desired modifications, mortar LCI's should be employed in the boat lanes to provide beach neutralization just prior to the time the first wave leaves the line of departure and during its run to the beach. They should precede the first wave by any desired distance, stop and lie to not less than 600 yards (minimum firing range) from shore, and continue mortar fire on the beach until the first wave is about 200 yards from shore. At this time the fire should be lifted about 200 to 500 yards inland and lifted in predetermined steps thereafter according to a prearranged time schedule based on anticipated troops advance. This type of moving close support was provided at Iwo Jima using 5"/38 AA Common fire with 1,200-foot second charges.
From: Commander Cruiser Division Thirteen
The enemy knew from the terrain that the landings would have to come on the southeastern or southwestern beaches. He planned his defenses to resist to the utmost the advance up the long axis of the island.
- He built defenses with an eye to naval gunfire, particularly to close fire. The terrain lent itself admirably. Few positions were built which could be reached by close-in fire because the trajectories were too flat at short ranges.
- He also built against bombing by constructing a surprising number of small strongpoints, interconnecting but individual, so that bomb damage would be confined to a small area. That is, he dispersed by multiplied defense positions.
- He played a very intelligent game in the use of weapons prior to and after the landing. He made all his guns count, seldom fired unless he had a good target; kept his flak positions concealed. He hid his mortars, antitank and inactive guns, until they could be used to advantage.
- Thus he concealed his strength so that on D-day the United States High Command was in a good deal of doubt as to what the opposition would be despite the longer period of softening up and the vast amount of effort expended in advance.
From: Commander Task Force Fifty-four--Commander Amphibious Group Eleven
It was obvious from the outset that the enemy defensive situation was one of the strongest yet encountered in this theater; that blockhouses, pillboxes, and caves were constructed and situated not only to meet a land attack but to withstand heavy naval gunfire. Moreover, the enemy must be credited with unusual and painstaking concealment of vital defenses and gun positions. Our intelligence photos were good but they could not be expected to show what neither the eye nor the camera lens could see.
Against such defenses, long or medium-range gunfire simply is not effective, and a tremendous amount of valuable ammunition can be wasted in general area fire. The reasons are twofold: First, the above mentioned concealment and camouflage make the location of targets possible only at very close range; above-target plan observation is not very effective for this purpose. Secondly, even when discovered, targets are so reinforced by a mass of earthworks that extremely heavy close range fire is required to uncover them before the essential job of destruction is begun; area fire seems to have had a very limited effect in this regard. Though a certain amount of general area fire is necessary initially to shake up the enemy and permit approach to closer ranges, doctrinal trust in neutralization fire may have to be revised.
The hard unpleasant fact must be acknowledged that direct hits must be scored repeatedly. This necessitates close point-blank ranges and acute observation. Naturally, this involves the threat of coast defense guns, but the risk of enemy hits may have to be accepted to do the job. At Iwo Jima enemy fire on our heavy ships was unexpectedly light even though firing positions less than 2,000 yards of shore were frequent after Dog-minus-3-Day. Observation of the medium
range bombardment executed on Dog-minus-3 showed little apparent damage.
From: Commanding Officer U.S.S. "Tuscaloosa" (CA)
It is believed that more attention and time should be devoted to training gun pointers and trainers in elementary pointer fire. Pointer fire appeared to be far below the peacetime standard of the old short range battle practices. The present emphasis in training is almost entirely on the various methods of director control which, of course, are the primary methods of shooting. However, well-pointed local control fire can be effective at close ranges, and occasion will arise when director control is not available.
From: Commanding Officer U.S.S. "New York" (BB 34)
The construction and positioning of defensive installations such as pill boxes, blockhouses, coastal batteries, and antiaircraft installations necessitated in every case a direct hit or many near hits to complete their destruction. Spotting on the 16th and 17th was by ship's planes and on the 18th range was closed to 1,750 yards, and spotting was by both plane and ship. The last day of bombardment was most effective because of the great facility with which targets could be identified and salvos could be spotted, and also because of the large quantity of ammunition expended on targets by the 14"/45 caliber and 5"/51 caliber batteries.
From: Commanding Officer U.S.S. "Nevada" (BB)
The enemy installations on Iwo Jima were very well camouflaged and of very heavy construction. The larger one could be destroyed or severely damaged only by repeated hits with the main battery. At ranges from 1,500 to 2,500 yards these targets could be distinguished by ship's spotters and gun pointers and trainers. Pointer fire was most effective as the fall of shot and results could be clearly seen. Most of the damage done to enemy installations by Nevada's gun fire was accomplished at short ranges with pointer fire.
The 40-mm. battery was used against a variety of targets including caves, suspected machine gun emplacements, light artillery emplacements and on one occasion against a small number of enemy personnel. The 40-mm. fire was believed to be effective only as a harassing agent. On the one occasion against enemy personnel, about six men were observed abandoning a damaged block house and were strafed with 40-mm. fire.
From: Commanding Officer U.S.S. "Pringle" (DD 477)
Fire support area was overcrowded and in the later phases wedged tight inshore between the transports. With a cross wind and current the problem of holding the proper heading was very difficult. The firing bearings at low elevations for the DD445 class are quite limited. To avoid having to swing ship with a loaded gun, it is necessary to consult some elaborate firing cam data before giving the order to load. No answer can be given to the problem, but to have the figures on hand, watch how the ship is swinging and load accordingly. The decrease in the rate of fire is unavoidable.
From: Commanding Officer U.S.S. "Van Valkenburgh" (DD 656)
During the bombardment, this vessel closed within 600 yards of the beach in order to pick up targets visually, but with little or no success. Targets were evidently well obscured and observation by the shore fire control party was very difficult, most of the time impossible. White phosphorus was used almost continuously, while it lasted, to aid the spotters. This vessel received no fire from shore installations, but observed some mortar and machinegun fire from the beach in other fire support sectors.
From: Commanding Officer U.S.S. "Bennett" (DD 473)
The commanding officer was distressed by the failure of ceratin "Oboes" and "Charlies" to realize the critical ammunition situation. On 22 February, between 0835 and 0910, this vessel, in accordance with instructions of the "Oboe", fired rapid four-gun salvos for preparation fire. The fire was unobserved. Three times the "Oboe" was informed of the continuing fire, and three times orders were received to keep it up. When fire was checked at 0910, a total of 587 rounds of AA common had been expended. It is realized
that a high rate of fire is necessary in preparation fire, but it is believed this expenditure was excessive for an unobserved area of doubtful targets.
On 27 February an "Oboe" ordered this vessel to fire one two-gun salvo per minute harassing fire) until further notice and then checked out of the net. He was off the net from 1235 to 1356. The commanding officer questions the wisdom of such a practice, not only because of excessive expenditure of ammunition, but also because of the danger of unobserved, uncontrolled fire near our own lines.
From: Commander Mortar Support Group 52.6 (Commander LCI Flotilla Twenty-one)
Plan ABLE consists of sustained fire covering a comparatively narrow target area and capable of extension in range. This plan is best adapted for close supporting fire (flank protection), harassing and interdiction fire. This plan of fire is delivered from a predetermined reference point around which the ships circle, delivering fire when the firing ship is headed toward the target area. The ships circle in both clockwise and counterclockwise movements, depending on the tactical situation.
Plan BAKER consists of a barrage fire covering a wide target area and capable of progressive movement in range. It is best adapted for neutralization fire and close support fire over and beyond our own troops. This plan of fire is delivered from a predetermined point with the ships that are firing disposed on a line of bearing parallel to the desired range median of the barrage or in line abreast formation.
Plan CHARLIE consists of independent or minor concentration fire covering point targets or targets of opportunity. It is best adapted for harassing fire, counter-battery fire, interdiction fire, and incidental destruction fire, particularly that requiring high trajectory. It is conducted by single or several ships whose fire may or may not be coordinated depending on assignment and is delivered from a reference point and bearing from the designated target area.
All target areas and fire plans in connection with the mission were contained in the Operations Plan, up to and including H-hour-plus-60. Subsequently, target fire and smoke missions were assigned.
At the outset of the mission it was assumed that preliminary naval and air bombardment had effectively silenced coastal defense and shore batteries that could possibly interfere with the carrying out of this group's mission. This assumption was subsequently found to be true. Sporadic mortar and machine gun fire was encountered however, which interfered with our operations on several occasions.
From: Commander Amphibious Forces, United States Pacific Fleet (Commander Joint Expeditionary Force)
GENERAL EFFECT OF NAVAL GUNFIRE BOMBARDMENT
Practically all enemy fixed installations capable of firing upon the landing beaches or transport areas and boat lanes were well covered and either destroyed or neutralized prior to How-Hour as evidenced by lack of opposition to the landing of first waves on all but RED Beaches. Many of the installations in caves or strongly reinforced positions were destroyed regardless of ammunition expenditure. A few fixed installations were later put back into commission and caused trouble for short periods.
The following lessons are either new or received additional emphasis at Iwo:
- Enemy mortars are very difficult to locate and destroy.
- Indirect naval gunfire is inaccurate when firing to hit on hill tops with indirect fire. This is because of long range and unknown inequalities of terrain.
- Guns emplaced in caves are difficult to destroy even when location is known.
- Observation of SFCP's is inaccurate in rolling and irregular terrain, and when greatly displaced laterally from the gun-target line. The SFCP's should therefore be located on the highest points, and as close as possible with respect to the gun-target line.
- Enemy powder produces little or no smoke and flame. SFCP's planes and ships therefore have difficulty in locating enemy guns. On the other hand, our powder causes much smoke and flame, both afloat and ashore.
- For destroying heavy emplacements and other vertical targets, very short range deliberate fire is required. This does not mean that long
range plunging fire is not advantageous under certain other condition.
Ammunition Resupply and Expenditure Data
The following table gives the amounts of ammunition replaced and expended at Iwo Jima:
* LCI(M)'s departed D-plus-12.
Resupply 16" HC 14" HC 12" HC 8" HC 6" HC 5" AAC 5" Star 5" Rkt 4".5 BR 4".2 Mor From assault ships 5,400 27,500 1,500 32,000 From AE's and AKE's 400 1,300 2,750 46,000 4,800 Total resupply 400 6,700 2,750 73,500 6,300 32,000 Expended 16" HC 14" HC 12" HC 8" HC 6" HC 5" AAC 5" Star 5" Rkt 4".5 BR 4".2 Mor D-minus-3 to D-day 3,300 1,000 3,500 1,900 14,000 200 D-day 1,950 1,500 400 1,700 2,000 31,000 1,500 12,000 8,000 20,000 D-plus-1 through D-plus 17* 450 900 6,200 4,500 102,000 13,000 2,000 50,000 D-plus-18 to D-plus-35 300 5,000 3,000 Total expended 2,400 5,700 1,400 11,700 8,400 152,000 17,700 12,000 10,000 70,000 Tons
Total tons 14,250.
2,280 3,640 520 2,020 440 4,160 270 145 875 Statistics Average daily rounds of call and harassing fires D-plus-1 through D-plus-17 26 53 0 341 265 6,000 765 0 118 4,550
It is interesting to note that a total of 14,250 tons were fired at Iwo Jima as compared with 10,965 tons at Saipan.
[B L A N K]
HEAVILY PROTECTED DEFENSES DESTROYED BY
DELIBERATE CLOSE RANGE NAVAL GUNFIRE
Reinforced Concrete Pill Box
Pillbox With Machine Gun.
Covered Artillery Position.
Reinforced Concrete Gun Position.
Covered Artillery Position. Note Concrete and Planted Grass.
Battery at Base of Suribachi.
Battery at Base of Suribachi.
Coastal Defense Gun.
Reinforced Concrete CD Emplacement, TA 182X D-Plus-14.
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