Climaxing an extended period of unrelenting pressure on the enemy, the capture of Okinawa marked the nearing of final defeat for Japanese land and air forces, just as the battle for Leyte Gulf in October 1944 had proved the death knell of the enemy fleet. Operation ICEBERG was one of the most successful amphibious operations ever conducted. Admiral R.A. Spruance, Commander Fifth Fleet, in charge of the Okinawa invasion, declared: "For the first time in history a fleet steamed to the threshold of an enemy homeland and, with its own air force embarked, stayed there at sea for a period of months until our own land and air forces were firmly established on the enemy's doorstep."
Operation ICEBERG: The Okinawa Campaign
The Forces Involved--Staging Logistics
Strategically, Okinawa, largest of the Ryukyu Islands, or Shoto Nansei, afforded a number of advantages. It lay but 350 miles from Japan's mainland, to which attacks could be launched covering both the islands and their sea approaches. Okinawa likewise would give our forces bases supporting further operations in the eastern China Sea for severing Japanese air and sea communications between the homeland and the mainland of Asia, Formosa, Malaya, and the Netherlands East Indies.
Admiral Nimitz published his preliminary order for the capture of Okinawa on 9 October 1944, establishing landing date L-day as 1 April 1945. Admiral Spruance was named commander of the expedition. Vice Admiral R.K. Turner commanded Task Force 51, the Joint Expeditionary Force. Expeditionary troops were under command of Lieutenant General Simon B. Buckner. Vice Admiral M.A. Mitscher led the Fast Carrier Force. Planning for Iwo and Okinawa proceeded concurrently.
The complex nature of the operation required extensive coordination of components of Army, Navy, and Marine Corps on both operational and logistic matters. The first of a series of joint conferences was held 1 November 1944. At that time the Commander Amphibious Force Pacific, Vice Admiral Turner, stressed the desirability of neutralizing outlying islands and obtaining an anchorage in the vicinity of Okinawa prior to the main landings, where logistic support of the fleet could be rendered. Kerama Retto, 20 miles west of Okinawa, was decided upon.
On 31 December 1944, Admiral Nimitz's Operation Plan 14-44 was issued, followed on 3 January 1945 by Spruance's more detailed Operation Plan 1-45. Projects were developed for three phases: The capture of Kerama Retto and the southern portion of Okinawa; the occupation of the remainder of Okinawa and capture of Ie Shima; capture of additional islands in the Ryukyus.
Admiral Spruance, in the Indianapolis, commanded the Iwo Jima assault during February. By 5 March, when it was apparent that the critical period of that operation was over, he retired to Ulithi to complete plans for Okinawa. Task Force 48 reached Ulithi from Iwo 4 March and during the next 10 days completed the necessary upkeep and replenishment prior to sortie on the 14th.
For logistic preparation, mounting, and rehearsals the principal forces assembled at widely separated places: The Fast Carrier Force at Ulithi, with the Gunfire and covering Force and Minesweeping Groups; the Northern Attack Force at Guadalcanal; Southern Attack Force and Western Islands Attack Force at Leyte; Demonstration Group at Saipan; Task Group 51.3, the Floating Reserve, at Espiritu Santo; and the Area Reserve at Noumea. The Northern Attack Force, after assembling at Guadalcanal, completed its final logistics at Ulithi from 21 to 27 March. The Area Reserve was not called into action.
Two special groups, Service Squadron Ten, Commodore W.R. Carter, and Service Squadron Six, Rear Admiral Beary, serviced our naval forces. Commander Service Squadron Ten, as heretofore, was charged with the logistic responsibility for the fleet at forward area bases, and the routing and sailing of service ships required by the forces operating in the combat area. Commander Service Squadron Six, brought in to give service at sea in specific operations the first of which was Iwo Jima, commanded a force of fleet logistic ships in the combat area, coordinated fueling schedules for fast carrier task forces, and exercised direct command of replenishment activities at sea.
As preliminaries to the operation commenced, Japanese naval power had been reduced to such an extent that its only surface threat was likely to be in raids on our supply routes or morning-twilight attacks upon our transport area. It was felt that Task Force 48, operating to the north and east of Okinawa, could intercept any enemy force approaching from Japan. It was necessary, however, to be ready to prevent any "express runs" from islands to the north, either to reinforce or to evacuate Okinawa. Accordingly, the fire-support ships of Task Force 54 and escort carriers of Task Group 52.1, in addition to other duties, could be employed to meet these runs if necessary. Actually the enemy made no attempt to interfere with our pre-L-day operations with his surface forces, or to evacuate or reinforce his troops. The only surface actions were with small craft. No shore battery opened on our ships prior to landings, even when mine sweepers were clearing mine fields within range of enemy guns. The Japanese evidently hoped to keep their skillfully camouflaged coast-defense guns intact in order to oppose the landing. Most of these positions, however, were located, heavily damaged, or destroyed before they could be effectively used. At Ie Shima, however, concealment of equipment and dispositions was carried to such effective extremes that our air observers, who flew over the island day after day at tree top level, picked up almost no signs of human activity prior to the assault.
The enemy's air force appeared to be his most formidable weapon. Because of the proximity of Okinawa to empire territory, it was possible to use the entire home-based air force against us. It was imperative therefore that we neutralize enemy airfields, particularly in Kyushu, Formosa, and the Nansei Shoto, to maximum extent so as to control the air of the Okinawa area prior to landing. Immediately after sortie from Ulithi on 14 March, Task Force 48 undertook this mission.
Exceeding all estimates, the greatest of our naval losses came from enemy suicide attacks. Between 14 March and 27 May, on which date operational control passed from Fifth to Third Fleet, 200 ships of the Fifth were victims of such attacks, 19 being sunk out of a total of 292 damaged by all causes.
On 18-19 March the Fast Carrier Force struck airfields and installations on Kyushu, at Kure, and in the Inland Sea area. On the 23d, as invasion forces were en route to the objective, the carrier force began the first of a series of strikes on Okinawa. On the 26th the campaign opened with landings on Kerama Retto by the Western Islands Attack Group. Despite narrow beaches and difficult terrain, all were quickly
accomplished against light opposition. Salvage and repair facilities were immediately set up in ships accompanying the assault forces. The destroyer Kimberly, hit by a suicide plane early in the morning, was the first to undergo repairs at the newly acquired anchorage.
Meanwhile the Amphibious Support Force under Rear Admiral W.H.P. Blandy, had arrived and opened day and night bombardment on Okinawa. Two fast carrier groups did the same, while two others refueled and rearmed. On Easter Sunday morning, 1 April 1945, the Tenth Army--96th and 7th Infantry Divisions, First and Sixth Marine Divisions--made the initial assault over the Hagushi beaches at Okinawa, capturing them with little opposition, making it possible to secure both Yontan and Kadena airfields by midday.
As fighting increased in intensity from day to day, it became evident that the Japanese had withdrawn to well-defended positions suitable for delaying-action tactics. Indicative of the ferocity of the struggle was the action at Sugar Loaf Hill, which changed hands 10 times before it was finally secured by the Sixth Marine Division. There was long bitter fighting everywhere. Our troops were forced to dig in and blast each fortified enemy position before organized resistance ended on 21 June, 82 days after that memorable Easter Sunday. Meantime, troops of the 77th Infantry Division, which had previously secured Kerama Retto, landed on Ie Shima 16 April. Organized resistance ended on the 22d, and shortly thereafter our planes were using the airstrip.
The Invasion Forces. As the war in the Pacific continued, despite Japanese losses and our consistent forward gains, or most vital concern was correct planning and the avoidance of failure to estimate properly the forces required for undertakings still to come. Operation ICEBERG was such a problem. Okinawa itself, entirely a coral formation 70 miles long, with one big town--Naha--at its southern end, though known as "typhoon crossroads" because of its evil weather, appeared superficially to present no greater difficulties than many we had already overcome. Yet when all its special aspects were clearly thought out, it totaled up to no less than 548,000 men of all arms, 318 combat ships, and 1,139 auxiliary vessels for the campaign, without counting the landing craft (boats, tractors, DUKWs, etc.) necessary to put our troops ashore.
By far the largest number of ships was assigned to Turner's Task Force 51. It was composed of a Western Island Attack Group, Task Group 51.1, under Rear Admiral I.N. Kiland; a Demonstration Group, Task Group 51.2, commanded by Rear Admiral Jerauld Wright; Rear Admiral Blandy's Amphibious Support Force, Task Force 52; Rear Admiral L.F.
Reifsnider's Northern Attack Force, Task Force 53; the Gunfire and Covering Force, Task Force 54, commanded by Rear Admiral M.L. Deyo; the Southern Attack Force, Task Force 55 of Rear Admiral J.L. Hall; and all expeditionary troops, designated as Task Force 56, commanded by Lieutenant General Simon B. Buckner. In all, Task Force 51 was composed of 1,213 ships, including assault shipping and vessels of the first Garrison Echelon.
Vice Admiral Mitscher's Task Force 58, the Fast Carrier Force, at first consisted of 9 large and 9 small carriers, 8 battleships, 2 large new cruisers, 2 heavy cruisers, 11 light cruisers, and 48 destroyers. By 1 May, however, its strength had been somewhat reduced by battle damage, 1 destroyer and 1 heavy cruiser added, so the force stood at 7 large and 8 light carriers; 6 battleships, 3 heavy, 2 large, and 11 light cruisers; and 49 destroyers. The carrier Shangri-La had joined during April, but Enterprise, Intrepid, and Hancock were forced to withdraw for repairs. The Cabot, light carrier, went back to Pearl for overhaul. The battleships North Carolina and New Jersey had retired for scheduled overhaul and replenishment.
Rear Admiral Beary's Logistic Support Group, Task Group 50.8, consisted of 1 light cruiser-flagship, 6 carrier escorts, 12 destroyers, 28 destroyer escorts, 39 oilers, 1 cargo ship, 4 ammunition ship, and 4 fleet tugs. Other special groups operating under Task Force 50 were a search and reconnaissance group of 6 large and 8 small seaplane tenders, and an antisubmarine warfare group of 2 carrier escorts and 13 destroyer escorts. Service Squadron Ten ships at various bases were designated as Task Group 50.9. A small British carrier force supported the Okinawa operation and was known as Task Force 57. Except for bulk petroleum products, the U.S. Navy was not responsible for the logistics of the British Force.
The Okinawa operation represented the first attempt to provide complete support for the fleet at sea on a broad scale over an extended period. Rearming and food replenishing had been proved practicable provided reasonably satisfactory sea and weather conditions prevailed but because of the number of service force ships and personnel required for complete support, only the fast carrier force received such at-sea servicing at this time.
Development of Logistic Facilities
All groups of that force were unanimous in praising the services
rendered at sea by the Logistic Support Group. The problem of supplying the units of this group which supported the force at sea, however, rested on the shoulders of Commander Service Squadron Ten at Ulithi, and upon his representatives at various forward bases.
The west coast, the Hawaiian islands, the Marianas, Marshalls, Carolines, South Pacific area, and Leyte provided bases for logistic support of the assault forces prior to participation in ICEBERG. Guam, Saipan, and Tinian were important as the advanced bases nearest the objective, but the major part of Fifth Fleet logistics came from Ulithi, which served not only as a staging area but the principal place of resupply. After logistic requirements had been estimated, but about 90 days before the target date, conferences were held with Service Force Pacific representatives and supply officers in the various areas, the estimates were made, were checked against stock on hand at mounting points, and requests were submitted for the deficiencies shown.
At Leyte, where two large groups assembled, there were no shore supply installations when our forces were mounting, all issues being made from Squadron Ten supply ships. Forces mounted in the South Pacific staged through Ulithi, where vessels were topped off with water, fuel, and provisions by arrangement with Commander Service Squadron Ten.
During the spring of 1945 Squadron Ten's facilities expanded in proportion as our fleet grew more formidable. During 17 March vessels added were: 2 landing-craft repair ships; 4 gasoline tankers; 3 provision store ships; 5 ocean tugs, auxiliary; 1 unclassified vessel; 1 hospital ship; 1 ammunition ship; and 1 salvage vessel. April brought more: 2 rescue tugs; 2 gasoline tankers; 3 provision store ships; 3 landing-craft repair ships; 3 cargo vessels; 1 oiler; 5 auxiliary ocean tugs; 1 ammunition ship. The May additions were 2 old ocean tugs; 1 rescue tug; 3 auxiliary ocean tugs; 1 landing-craft repair ship; 2 provision store ships; 1 gasoline tanker; 1 fleet tug; 1 battle-damage repair ship; 3 attack cargo vessels; and 1 cargo ship. All vessels participating in the Okinawa assault were instructed to load to capacity with everything needful, and to stretch their storage space as much as possible to meet the demand.
Nearly all ships of the Southern Attack Force and the Western Islands Attack Group for the Okinawa operation assembled and loaded at Leyte. Initial plans designated Commander Service Force Seventh Fleet as the
responsible service agency, and Commander Amphibious Group Twelve as responsible logistically for servicing the ships of the Joint Expeditionary Force staging at Leyte. When it became apparent that Seventh Fleet could not supply the needs of this force, Commander Service Squadron Ten's Representative A, Captain Ogden, was ordered from Kossol Roads to provide services for Nimitz's ships in the area. ComServFor Seventh Fleet provided additional services as requested by Captain Ogden.
Arriving 15 February 1945 in the Argonne, Captain Ogden reported to Rear Admiral J.L. Hall, Jr., commanding Amphibious Group Twelve. Pending arrival of additional service-force units, conferences were held to obtain an over-all grasp of the problems involved. It was determined that sufficient quantities of everything required were either available or could be made so at Leyte. All ships had to be provisioned before the training and rehearsal period, and topped off just before departure to the objective. Schedules were interrupted by foul weather and the late arrival of some of the ships from Iwo Jima. The distances from troop embarkation points to the logistic anchorage, 15 to 30 miles, added to the problem.
Maintenance facilities available to staging forces were the destroyer tenders Dixie and Markab; one limited repair ship, the Argonne; two repair ships, the Hector and Prometheus; one internal-combustion-engine repair ship; and two floating drydocks. Two landing-craft repair ships, Egeria and Endymion, which were assigned to the amphibious group, were available after 1 March. Because of the limited time in which to accomplish essential repairs and the length of time required to load ships, it was decided to place one repair ship in each of the two loading areas so that a maximum of work could be accomplished prior to departure. Work on small craft was undertaken by three of the other repair ships.
The total number of ships to be serviced at Leyte was 432, some--ships newly reporting from the United States--needing little attention, others considerable, especially amphibious craft returning from Iwo Jima. Of the floating drydocks, both brought forward from Kossol, ARD-16 was unavailable for the staging work because it contained a battle-damaged destroyer, the Renshaw. Consequently ARD-17 carried most of this type of work, with Seventh Fleet facilities used on several occasions. To complete what would normally be the necessary drydock work every available diver was used. Because of experience gained with many small ships in this staging, a definite need was indicated of having
small drydocks of 1,000 tons and pontoon docks to reinforce the 3,500-ton ARD's.
Because of a lack of replacement ships, permanent battle-damage repairs had to be made on the net-carrying ship Keokuk, and major hull repairs on the attack cargo ship Starr and the amphibious flagship Estes. The Keokuk was alongside the Markab from 11 to 18 March, with 9,700 man-hours spent on repairing damage sustained by a suicide plane hit 21 February. The Starr suffered severe damage to hull plating and framings, and to fittings above the main deck, as a result of pounding her side while transferring ammunition to cruisers alongside at Iwo. The Dixie and Hector made the necessary repairs between 12 and 18 March. The Estes had a rupture in her fresh-water tank about 8 feet long by 2 feet wide; in 72 hours the Dixie patched it up sufficiently to enable her to leave with the fleet.
An acute shortage of spare parts developed at this time. Those on hand were rationed out, more flown in from Ulithi and Pearl, and as many as possible obtained from Seventh Fleet, with a few from the Egeria and Endymion on their arrival from Iwo. Spare-parts barge YF-624 came in 13 March, partly relieving the situation, but practically her entire cargo was needed to complete repairs to inoperative equipment, leaving virtually none for replacing "on board" spares.
Fresh, frozen, and dry provisions came from ships reporting to Captain Ogden. Allocation of quantities was made on the basis of the personnel to be fed; distribution was effected by anchoring ships to be supplied near provision ships in the logistic anchorage. The supply was adequate, if not all that was desired. Except for manila rope, general stores were available in adequate quantities from store ships. The LSM's had priority for lines of 5- and 6-inch size, while other ships received only sufficient to meet their minimum requirements. On 16 March a dispatch was sent to Commander Service Force Pacific requesting that 200 coils of 6-, 7-, and 8-inch line be sent to Okinawa. All available was immediately shipped, but the amount received was less than requested and required. Water supply was provided by one water tanker for smaller vessels not equipped with evaporators and from a water-supply point on South Samar at which four LST's could water simultaneously from an extended pipe run out to mooring dolphins.
Steam vessels were fueled to capacity with black oil by tankers in the logistic anchorage prior to departure. Diesel-driven craft were also filled to capacity; LST's acted as fueling ships for smaller craft until the amount left on board was reduced to 100,000 gallons. Fog oil, smoke
pots, and smoke floats were in adequate supply; all ships drew their allowance, plus as much more as they could load. During the first week in March a number of Squadron Ten ships were sent to Leyte to fuel the staging vessels. On 2 March the Abarenda left Ulithi with 58,000 barrels of Navy special fuel. Next day the Monongahela, Cimarron, and Manatee also left with combined cargoes of 286,000 barrels of Navy special, 13,000 barrels of Diesel, and 1,109,000 gallons of aviation gasoline. The same day the YO-46 left for Leyte with an additional 10,000 barrels of fuel. On the 4th the Suamico, Neches, and Cacapon, with the merchant tanker Hanging Rock, left Ulithi for Leyte with 296,000 barrels of Navy special, 112,000 barrels of Diesel oil, and 948,000 gallons of aviation gasoline.
Ammunition was brought from Ulithi in naval and merchant ammunition ships, also at Leyte there were several Seventh Fleet ammunition carriers. In addition, 17 attack transport cargo ships and 40 LST's which loaded at Leyte carried some of the deadly stuff to Okinawa as replenishment for fire-support vessels.
The Northern Attack Force, Task Force 53, mounted for Okinawa in the Guadalcanal-Russells-Purvis Bay area. This was the last and largest staging operation conducted in the South Pacific, an area already engaged in roll-up activities. Logistic support was provided by Commander Service Squadron South Pacific Force and Commander Naval Bases South Solomons, coordinated by Rear Admiral L.F. Reifsnider, Commander Amphibious Group Four. Two periods, 17-28 February and 8-15 March were allotted for logistic and maintenance support in the South Pacific, while 21-27 March was scheduled for topping off and necessary voyage repairs at Ulithi. Admiral Reifsnider in the Panamint interrogated the various commanders and a final logistic program was prepared. With the exception of 17 ships--12 attack transports, 3 attack cargo ships, and 2 LSD's receiving final logistics in the Russells--all other ships of the Northern Attack Force, 207 in all, were serviced at the Purvis Bay-Tulagi-Guadalcanal area. To handle this large force, Commander Service Force South Pacific had previously provided substantial increase of all stock levels at supply depots.
To augment repair facilities in the area, Commander Service Squadron Ten ordered Captain Paul B. Koonce, his representative at Manus in the
destroyer tender Sierra, to Guadalcanal as representative there for the staging period. With him went the internal-combustion-engine repair ship Mindanao, repair ship Briareus, and limited repair ship Zaniah, the group reporting on 21 February for temporary duty to Commander Service Squadron South Pacific Force. Other repair facilities sent to Purvis Bay, Florida Island, in the Solomons, during February for temporary duty were the battle-damage repair ship Aristaeus, landing-craft repair ship Coronis, repair ship Vulcan, and drydock ARD-14.
Repair facilities were adequate, and nearly all ships obtained full allowance of spare parts before departure. The LST's were the only group presenting serious maintenance or repair problems. Sixty of them reported from the Philippines for use with the Northern Attack Force, and Captain Koonce had conducted intermediate screening of their needs at Manus, 41 being selected to go to the amphibious forces at Guadalcanal. The group arrived late, and many were in urgent need of repairs. Despite the short time involved, however, all were ready to leave on schedule.
Movement toward the objective via Ulithi started 12 March, the remainder of the force leaving Guadalcanal on the 15th. Service Squadron Ten's repair unit was dissolved that day on departure of the Sierra and Mindanao for Ulithi. Zaniah went to Leyte; Vulcan departed for Noumea to join the floating reserve staging there in late March. Briareus reported to Espiritu Santo, where the area reserve staged, Coronis accompanied the Northern Defense Group to the objective, and Aristaeus returned to Ulithi 2 April.
A total of 235 ships moved from Guadalcanal to Ulithi, where final supplies were received during the 6-day replenishment period. A logistic plan like the one used at Guadalcanal was forwarded to Commander Service Squadron Ten at Ulithi prior to the departure of the Northern Attack Force, and by its use all ships were adequately provisioned, fueled, watered, and made ready for sea on time. Because of the work on battle-damaged ships at Ulithi, very little tender service was available to the force. However, only minor material casualties occurred, and repairs could be made by ships' crew, with limited assistance from repair ships.
Following the departure of the Northern Attack Force from Guadalcanal, April saw a drastic roll-up of logistic activities in the South Pacific. Fifteen different types of service ships were released to Commander Service Squadron Ten during the month. On 13 April the 90,000-ton floating drydock ABSD-1 at Espiritu was ordered to cease operations and prepare to move forward in sections to Leyte. Her first echelon
sailed 29 June, the remaining sections 7 July. Every such logistic step meant advance for us, retreat and bitter discouragement for Japan. There was no question of our ultimate victory; that was a matter of persistence and time. The end was in sight.
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