Chapter III. Air Support

From: Commander Amphibious Forces, United States Fleet (Commander Joint Expeditionary Force)

PRELIMINARY AIR BOMBARDMENT

Preliminary air bombardment of Iwo Jima was delivered by heavy horizontal bombers operating from the Marianas bases. A long series of area bombing missions were flown during the months preceding the landing. From dog-minus-Twenty this bombardment was conducted on the basis of target requests issued by Commander Joint Expeditionary Force. The principles involved in specifying the targets for preliminary air bombardment were:

  1. The neutralization of the airfields and installations on Iwo Jima.

  2. The destruction of gun positions and fixed defenses.

  3. Unmasking of additional targets.

Although the tonnage of bombs was large, no permanent results apparently were obtained. The southern portion of Iwo Jima is soft volcanic sand which easily craters but is just as easily smoothed out again. On the north it is rocky and has many steep ravines. The Japs were well dug in and only those bombs which hit the few exposed targets, or hit and penetrated protected ones, did any lasting damage. So far as can be determined the psychological gain from the prolonged bombardment could not be measured in terms of reduced efficiency on the part of the Japs on the day of the landing.

From: Commanding general, Headquarters Fourth Marine Division, Fleet Marine Force

Results indicate that high horizontal bombing by land based aircraft had little effect on the enemy's defensive system. In fact, one POW estimated that 40 percent of the bombs dropped by these aircraft prior to D-day missed the island entirely and this is considered a conservative figure. In order to permit more effective air strikes from low altitudes, which are essential if destruction of emplacements is to be accomplished, early destruction of enemy AA defenses must be effected. The efficiency of NGF [Naval Gun Fire] spotting by VOS [Observation Scout Plane] aircraft would also be enhanced by the reduction of the enemy's AA.

From: Commanding General, Expeditionary Troops (Task Force 56)

The prolonged aerial bombardment of Iwo Jima, which was a daily occurrence for over 70 days, had no appreciable effect in the reduction of the enemy's well prepared and heavily fortified defensive installations.

From: Commander Fire Support Unit Four (51.1.4) (Commander Cruiser Division Five)

On D-minus-2-Day, three flights of B-24's bombed Iwo from about 5,000 feet, the surface ships suspending fire during the runs of the B-24's. The first group received meager AA fire; but the second and third received moderate to heavy at times; though none of the planes were noticed to be in difficulty. On D-day, one group of B-24's (15 in number) bombed at about 4,000 feet while the ships continued their bombardment. By observation, no AA fire was delivered at the B-24's. This one group was the only attack in the 60 days of bombing delivered at low altitude. The surface ships could have coordinated their bombardments with the air bombings throughout this 60-day period; and it is estimated that many more surface bombardments could have been undertaken with the same surface composition. By this means, the major effort, which was in the B-24's, could have been greatly increased in accuracy and effectiveness.

From: Commander Amphibious forces, United States Pacific Fleet (Commander Joint Expeditionary Force)

Relative effectiveness of the weapons at the disposal of air were:

  1. Machine gun .50-caliber bullets.--These were the principal weapons of fighters of the ex-CAP [Combat Air Patrol]

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    and fighter spotters. Strafing was effective against exposed enemy troops and gunners but not against the many who were well dug in.

  1. GP [General Purpose] bombs.--These were the standard weapons of air bombardment. All of the enemy's above-ground installations were destroyed but his strong points resisted bombing.

  2. Napalm.--This new weapon has given excellent results in previous operations but at Iwo a large percentage of duds were observed. The cause of the duds is not known. The Napalm which ignited was apparently effective.

  3. Rockets.--The ability of rockets to hit and penetrate fortified positions was thoroughly demonstrated in this operation. Rockets were in constant demand and their use made them the most successful air weapons in the Iwo Jima campaign.

From: Commander Fire Support Unit Four (54.1.4) (Commander Cruiser Division Five)

In the period about 60 days prior to D-minus-3-Day, the B-24 force in the Marianas (search planes, night snoopers, and surface craft) operated against Iwo and its communications.

While there was unity of command in the higher echelon, by the time it reached the operational forces it was command by cooperation (though willing and good as far as it went). The surface forces conducted six heavy bombardments against Iwo, and one against Chichi Jima and Haha Jima. Ten medium tonnage ships of various types (DE, APD, LST, LSM, small AK, one trawler) were sunk or destroyed. The B=-24's bombed for about 60 consecutive days, releasing at 18,0000- to 20,000-foot altitude usually against AA fire. Once or twice a group of B-29's assisted. The night attack planes against shipping seldom located targets. The day search planes frequently reported convoys headed toward or away from Chichi Jima.

From: Commander Amphibious Forces, United States Pacific Fleet (Commander Joint expeditionary Force)

The planes used in supporting the Iwo Jima operation were furnished by CVE [Aircraft Carrier, Escort] and Fast Carrier Units. An innovation in this operation was the use of a specially trained Antisubmarine Patrol Squadron for day and night patrols. A CVE was devoted to this phase of air support. One night operations carrier was provided from Task Force 58 to supply dusk and night target combat air patrol. This carrier also provided a dusk and dawn, sweep to neutralize Susaki airfield, Chichi, Haha and Minami Jima. The escort carriers (TG 52.2) were divided into four units as follows:

The number of CVE's at the target area was as follows:

Direct air support operations Iwo Jima began on D-minus-Three with the arrival of TF 52 and 54. The Advance Commander Air Support Control Units was embarked in the Estes. This was the first operation in which the Advance Commander Air Support Control Unit worked from an AGC and with a complete team. The results were more satisfactory than in previous amphibious operations where it was necessary to operate from battleships or other naval vessels.

The pre-Dog-Day air support consisted of Combat Air Patrol, Anti-Submarine Patrol, direct support to Minesweepers and Underwater Demolition Teams, Smoking and Photographic missions, and heavy bombing strikes by land based Army aircraft. In addition, regular air support groups were available on schedule throughout the day for covering missions and called strikes.

TIME OF COMPLETING ASSIGNED MISSIONS

In almost all cases, an accurate record was taken of the time a mission was assigned, and the time it was completed. Following is a break-down of the times taken to complete assigned missions:

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Time of assignment to time of completion: Number of
missions
Under 15 minutes 66
15 to 30 minutes 67
31 to 45 minutes 33
46 to 60 minutes 8
Over 60 minutes 8
Unknown     6
  188

DIRECT AIR SUPPORT OF GROUND FORCES--CONTROLLED BY LFASCU

Commander Landing Force Air Support Control Unit assumed control of direct support aircraft at the objective on 1 March 1945 at 1000. Support aircraft assigned to shore-based control consisted of air coordinators, tactical air observers, strike groups, relieved combat air patrols and VOF [Navy observation fighter squadron] flights, and miscellaneous photographic, spray and other utility missions. Effective with commencement of operations from Maple Field 3 March, control was also exercised over land-based transport, evacuation, supply-drop and transient aircraft.

OY OBSERVATION PLANES

A total of 18 OY type observation planes were brought to Iwo Jima for VMO [Marine observation squadron] Squadrons 4 and 5. It was not possible to load planes for the Third Division at Saipan as originally intended. Six of these spotting planes were carried on the LST 776 which was equipped with Brodie launching and recovery gear. The second plane launched from the LST crashed into the sea because of a temporary failure of the launching gear. The remaining 12 planes were carried by 6 of the CVE's. (Two were lost in the sinking of the Bismarck Sea.)

From: Commander Amphibious Forces, United States Pacific fleet (Commander Joint Expeditionary Force)

COORDINATION WITH NAVAL GUNFIRE AND ARTILLERY

In spite of early misgivings, coordination between air support, naval gunfire, and artillery did not prove to be a major problem. Due to the small size of the objective and the close ranges fired by ships and artillery, it was very seldom necessary to use plan "VICTOR" or plan "NEGAT."

NAVAL GUNFIRE

During the early hours of D-day, a graphic plot of preplanned high-ordinate naval gunfire was available to SAD [Support Air Direction] control officers. This enabled them to direct strikes into areas that gunfire was not covering, or to hold planes to a safe minimum altitude. After the pre planned gunfire phase was completed, close liaison in the joint operations room was adequate for obtaining information on all missions that might have been endangered by high-ordinate gunfire. After control of high-ordinate rocket and mortar landing craft fire was passed from CTF 51 to CTF 53 (about D-plus-One), liaison on gunfire matters was not satisfactory. However, high-ordinate gunfire was used so seldom at this time that pilots experienced little difficulty in performing missions.

ARTILLERY

Accurate coordination with artillery was practically impossible because there was no Corps Artillery representative on the Eldorado. It was only the fact that there was so little high-ordinate artillery fire that enabled SAD officers to send planes on missions without a detailed check on artillery. Artillery communication in the joint operations room proved too slow and cumbersome in the few cases where plan "NEGAT" was requested. In one instance (mission No. 8 on D-plus-Two), it took 30 minutes to get a reply over artillery circuits to a request for a plan "NEGAT." The reply, when received, stated that another 25 minutes would be required to place "NEGAT" in effect. Since planes on station could not wait that long, they were directed on the mission. (In this case the SAD officer estimated that the artillery ordinate in the target area would not be too high to be dangerous). In a later request for plan "NEGAT" (mission No. 7 on D-plus-Three), much better results were made by contacting the Landing Force over ASC [Air Support Control] net. In this case, it took only 20 minutes to clear with Corps Artillery for a low-level Napalm and strafing attack.

The Iwo Jima operation marked the first time that the Brodie Sea Rig for launching and recovering small artillery spotting aircraft has been available for use in combat. This system, constructed

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on an LST, enables the LST to carry, launch and recover 6 to 10 small planes in addition to carrying a tank deck load of cargo. Prior to launching, the plane is suspended from a trolley mounted between 2 booms suspended clear of the ship's side 40 feet over the water. In launching, the plane runs the length of the trolley and trips a hook release; in recovery, the plane files parallel to the ship, hooking onto a trapeze loop, and is braked to a stop along the trolley. At Iwo Jima 5 of the 6 planes carried were launched successfully, but due to rough weather no recoveries were attempted by the LST and the planes were landed on the island.

From: Commander Amphibious Group Two (CTF 53 and CTG 51.21)

For the first time in an amphibious operation in this theater an Air Support Control Unit was landed and set up ashore with the intention of actively controlling close troops support missions. This unit was composed of marine and naval officers (with the former predominating) and marine enlisted technicians and operators. The liaison that this unit was able to accomplish by virtue of the proximity (75 feet) to the Landing Force Command Post far surpassed anything that has ever gone before in air support operations and as a result, troop requests for air support were run much more expeditiously than ever before. It is considered that a Landing Forced Air Support Control Unit is an absolute necessity for the control of troop support missions. However, it is felt that the Landing Force Air Support Control Unit tried to assume the control of close support missions before they had monitored all the nets long enough to get the routine and to pick up control without any lost motion. Some equipment difficulties entered into the picture since this was the first service use of the radios. It is felt that in future operations when the LFASCU is preparing to assume control of troop support missions, they should monitor all nets which they expect to operate for a minimum of 12 hours. At quiet periods, radio checks should be made. Net control officers expecting to join the LFASCU for the operation of the major strike nets (SAD-1, SAD-2, SAD-8, SAR, or SAO) should be embarked on the controlling AGC and the relief AGC. They should disembark after the close of operations one day and be ready to assume control on a thoroughly tested shore-based set-up early the following morning. Lost motion was noted particularly during the Iwo Jima operation in that when the LFASCU attempted to assume control of troop support missions that they did not have the complete current lists of air liaison parties' requests. After this hiatus was closed, however, the LFASCU did an excellent piece of work and in many cases gave the troops much more nearly what they wanted than was ever possible before the inception of this system.

A new method of coordinating artillery fire and air strikes was used successfully for the first time during this operation. A brief of each air strike was broadcast over the Corps Artillery Fire Direction Control net. Each air strike was given a number and the following information was given: Time bracket, target area, direction of approach and retirement, number and type of aircraft, minimum altitude and any other pertinent information. Each battery of artillery was able to control its fire so as not to interfere with strikes, but a complete shut-down of artillery was only necessary once or twice to run a treetop level Napalm attack. Whenever two or more battalions of artillery were firing on the same target, that information was passed to CASCU with the maximum ordinate and aircraft were warned to keep clear. This proved a very satisfactory method of coordination from the air support viewpoint and it is believed to be satisfactory from the artillery viewpoint.

Coordination with naval gunfire still can only be obtained (after fire support has been turned over to the shore fire control parties) by placing "Plan Victor" (limit of maximum ordinate at 1,200 feet) in effect, thus imposing a minimum altitude limitation on the air strike. Fortunately naval gunfire ordinates at the ranges most commonly used are below 1,200 feet and {Plan Victor" does not impose a serious limitation. But the minimum altitude restriction on the air strike places a considerable limitation on the aircraft since bombing and strafing accuracy is greatly increased with decrease in dropping and firing altitude.

In general, communications were excellent on all air support nets on the flagship of TF 53. This ASCU played an important role in maintaining, by relay, communications between other air support participants. On several occasions

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this unit assumed complete control of various nets during periods of matériel failure in other units. At night considerable CW interference reduced the efficiency of the high-frequency circuits. Numerous instances still exist of aircraft and other stations using the improper net, and of not maintaining good radio discipline on the correct net. Air liaison parties showed evidence on numerous occasions of not being familiar enough with their radio equipment. Both carrier and target antisubmarine patrol being on the same frequency was the cause of considerable interference.

RECOMMENDATIONS

This ASCU was composed of 15 officers and acted as a relief team during the Iwo Jima operation. Considerable difficulty was experienced in adequately monitoring all nets, and still having officers available to relieve others for meals, etc. From this experience, it is felt strongly that the minimum number of officers that a complete operating Air Support Control Unit can function with is 19. Seventeen of these are required for the operating team, including net control officers, communications officers and intelligence officers. Once trained, this team is an intradependent, cooperating unit which cannot afford to have any member on call to any outside source. All planning and over-all jurisdiction of operations must be done by officers who are not a part of the operating team itself. The organization of new strikes, formation of plans for the following day, changes in existing plans and other strategic problems must be worked out by officers who are intimately familiar with, but not involved in, the working of the operating team itself. The planning staff is composed of the ComASCU and the planning officer and is required in the ASCU on the flagship having control of an amphibious operation. No planning staff is required on relief flagships unless it is contemplated that they assume control without being able to transfer any officers from the controlling ASCU.

From: Commander Task Unit 52.2.5 (Commander Carrier Division Seven)

The night carrier mission was primarily to protect the occupation force on Iwo Jima, and its surface support units, from enemy air attack at night. The secondary mission was the daily dusk observation and neutralization of Susaki Airfield, Chichi Jima, the enemy's only nearby airfield from which an attack could be staged against Iwo Jima. (See photographs in pt. IV.) In the event of an enemy surface effort to relieve the hard-pressed Iwo Jima garrison, the destruction of such surface units would immediately become the primary mission of the night carrier group, in conjunction with the day-operating CVE's of the Air Support Group.

To accomplish the mission set forth above the night carrier duties involved:

From the nature of these duties it will be seen that the Enterprise maintained a continuous 24-hour air-operations schedule during a large part of this period.

The pilots flying target night CAP over Iwo Jima complained that the VHF channel Dog was very crowded, especially during the early evening hours of the first days of the occupation. Some confusion on the part of the amphibious FDO [Fighter Director Officer] was evidenced by the large number of interceptions of friendly surface contacts, largely on occasions when the screen became saturated. As the operation progressed, however, fighter direction at Iwo Jima soon became more efficient though no "splashes" were achieved.

From: Commanding Officer U.S.S. "Petrol Bay" (CVE 80)

There were also instances where the squadron support groups commenced runs on a target designated by CASCU only to find another strike coming in on the same target area from an opposite direction. This situation may have been due to the fact that some support groups were left under the control of their own flight leaders while other groups were controlled by the air coordinator.

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NAPALM BOMBS

From Commanding Officer U.S.S. "Randolph" (CV-15)

Bombs and fuzes used by Randolph aircraft functioned without any known deficiencies. Napalm bombs were a distinct exception, the estimated observed functioning being from 30 to 50 percent of those dropped. A part of the difficulties may be attributed to the rocky nature of the terrain at Iwo Jima, the only place where Napalm bombs were used.

From: Commander Task Group 51.17, Commander Task Group 51.26 and Commander Task Unit 52.2.3 (Commander Carrier Division Twenty-five)

Replacement pilots received during the operation were so inexperienced that they could not be used as replacements. All were returned to Guam for what is hoped to be a refresher period. With their present training and experience these pilots are of no value as replacements and only take up critical living space aboard ship. It is again recommended that this matter be corrected.

From: Commander Task Unit 52.2.1 (Commander Carrier Division Twenty-six)

The limiting factor in the endurance of CVE's furnishing direct support during a landing operation was proven to be aircraft bombs and rockets. When the operation progressed beyond Dog-plus-Ten-day, ships of this unit were depleted of all aircraft armament except a very few 500-pound SAP [Semi Armor Piercing] bombs and their original number of depth charges. A jury rig pick-up and delivery service of aircraft rockets by a destroyer of the screen was inaugurated but this was slow and painful replenishment, and did nothing to alleviate the destitution of bombs.

From: Commanding Officer U.S.S. "Natoma Bay" (CVE 62)

Innumerable criticisms of radio discipline have been written with no marked improvement. The root of the trouble apparently lies in the fact that VHF transmissions are considered secure, that there is absolutely no reluctance to make unnecessary transmissions, and that there is far too much traffic assigned to four channels (the ten channel VHF should correct this latter complaint.) Ships and planes alike are offenders on all counts.

On support missions the support planes should have a free channel, particularly when timed close support missions are in progress. Under these circumstances a sample of the traffic heard while trying to organize a strike is given:

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