Iwo Jima 1945 Page 4
Airfield 1 1st Battalion, 145th Infantry
Each sector was reinforced by Naval Land Force units, coastal defence troops and antiaircraft units.
The Japanese defences on Iwo Jima and the deployment of the main infantry units.
The Japanese had concentrated a large part of their efforts in covering the beaches, deploying artillery and mortars at each end. Anti-tank ditches had been dug to funnel tanks onto minefields while more mines protected bunkers and pillboxes. It was clear from the aerial photographs that the number of fortifications had more than doubled between December 1944 and February 1945, in spite of the air raids. It also appeared that the Japanese had prepared a new defensive line across the centre of the island. It ran diagonally from Hiraiwa Bay on the northwest coast in a south-easterly direction to the high ground north of the East Boat Basin.
The additional fortifications meant only one thing: that there were far more troops on Iwo Jima than anticipated. The Japanese had been reinforcing Iwo Jima by sea and on 6 January intelligence officers increased their estimate of the garrison to over 13,000 troops. The new outline of the Japanese Order of Battle was as follows:
• 4720 men of 2nd Mixed Brigade, 109th Division, commanded by Major-General Koto Osuka
• 3950 men of 145th Infantry Regiment, commanded by Colonel Masuo Ikeda
• 2 anti-tank gun battalions and a mortar battalion with 1650 men
• A detachment of the 26th Tank Regiment with 350 personnel, 30 medium and 10 light tanks
• The Iwo Jima Naval Guard Force with 1750 men
• 400 naval airbase personnel and 700 airbase construction personnel.
Intelligence also assumed that Lieutenant General Tadamichi Kuribayashi had overall command of the Defence Sector covering the Volcano and Bonin Islands – part of the Nanpo Shoto Islands – and that he controlled it from 109th Division Headquarters on Chichi Jima. It also supposed that Major General Osuka was in charge of preparing Iwo Jima’s defences.
While V Amphibious Corps always referred to Iwo Jima as ‘Island X’, there was a serious security breach on 22 December 1944. The Honolulu Advertiser printed an illustrated article on US Air Force bombing raids and noted that the target was Iwo Jima. Anyone studying operational photographs could see that the two photographs accompanying the article were of Island X. V Amphibious Corps responded by putting out information that the recent build-up of ships and troops were preparing for an attack on Formosa. It made no difference to General Kuribayashi’s defensive plans; his men continued to dig themselves deep into Iwo Jima’s rocky terrain.
FOREWARNED
Japanese submarines had shadowed Task Force 51’s build up in the Marianas and reported its journey towards Ulithi to Tokyo. Japanese Imperial Headquarters was sure that Iwo Jima was the likely target. On D-10 Tokyo warned 109th Division headquarters of an imminent attack and gave the size and composition of the invasion force to General Kuribayashi.
Logistics and Administration
A successful invasion had to be supported by a well planned logistical operation. The troops ashore had to be supplied with ammunition, food and water, while the wounded needed to be evacuated quickly. Landing Ships had to bring everything to the waters off Iwo Jima ready to be transferred to landing craft and delivered to the beach. The Marines could then haul what they needed to the front line. The same applied to evacuating the wounded, in reverse.
While Fleet Marine Force, Pacific, had prepared outline logistical plans, General Schmidt’s staff began working on the details as soon as V Amphibious Corps took over. Their final plan involved three different Pacific-based logistic organisations. Fleet Marine Force’s Supply Service would supply the Marines with ammunition, equipment and supplies. The US Army Forces Quartermaster would supply Army troops with ammunition, supplies, equipment; it would also supply rations for Marine and Army units. The Navy’s Service Force would provide fuels and lubricants for all units ashore.
Once the amtracks had delivered the Marines to the shore, they were kept busy ferrying supplies to the front line and returning with injured men. Twin-mounted machine-gun turrets kept snipers at bay. (NARA-127-GW-109691)
Supplies were delivered to Saipan and then packed onto ships; some were loaded onto amtracks and DUKWs ready to be driven ashore. During the battle they would wait offshore until the supplies were required and then be loaded onto landing craft and ferried to the beach. There were no offshore reefs, so all types of landing craft could carry supplies direct from the transports to the beach. Colonel Leland S. Swindler, the Landing Force Shore Part Commander, then had the job to make sure that 8th Field Depot coordinated the division shore parties. The danger was that stores would clutter up the shoreline, creating a dangerous logistical bottleneck and an inviting target; they had to be moved inland as soon as possible. If all else failed, V Amphibious Corps’ Air Delivery Section was on standby to make emergency air drops to front-line troops.
Five Provisional Amphibian Truck Companies equipped with DUKWs had been assigned to V Amphibious Corps; 4th and 5th Marine Divisions had one each and three were Army units. Two new transport vehicles had also been made available and while the Clever-Brooks amphibian trailer could carry a 3.5-ton load, the M-29C Light cargo carrier, or Weasel, was capable of hauling a half-ton load.
There were concerns that wheeled vehicles would not be able to carry supplies off the beach and several contingency plans had been prepared. Supply pallets would be stacked on runner sleds so that tracked vehicles could drag them off the beaches. Steel matting was also provided to create temporary roads. Steel planks, called Marston matting, were normally used for temporary airstrips but hundreds had been hinged together in groups of seven, ready to be stretched out across the beach to form temporary track ways. A total of 8.5 miles of Marston matting was prepared in the Pearl Harbor Navy Yard.
Landing Ship, Mediums (LSMs) would carry five Sherman tanks each directly to Iwo Jima’s beach so they could drive straight onto the shore. The tanks had been fitted with exhaust and air intake vents in case the landing ships could not get right to the beach and they had to drive a short distance through shallow water. The first tank company to land close to Mount Suribachi was carried by a Landing Ship, Dock and three much smaller Landing Craft, Tank (LCTs) transferred them to the shore.
While each division had its own organic engineer battalions, 133rd and 31st Naval Construction Battalions, known as Seabees, had been attached to 4th and 5th Divisions. Engineers would have to clear mine fields and obstacles, build roads and facilities and establish water supplies. They would also be called upon to support the Marines, using their demolition skills to destroy bunkers and emplacements. V Amphibious Corps also had a number of specialist engineer units to deal with bomb disposal and mapping.
The Japanese airfields had to be repaired and improved and work would commence as soon as they were captured. 62nd Naval Construction Battalion had to open Airfield 1 as soon as possible for observation planes and fighter aircraft while 31st Seabees would repair Airfield 2 and extend it to 7000 feet, ready to receive crippled B-29s returning from Japan.
One thing that V Amphibious Corps was sure of, there would be high casualties, both during and after the landings, and the wounded had to be evacuated and treated quickly to maintain morale. Each of the divisional medical battalions had 144 beds and V Corps had an extra medical battalion; it also had Evacuation Hospital Number 1 and 38th Field Hospital. The corps could care for 3160 casualties while 8th Field Depot could look after another 1500.
Once patients were well enough to travel, small Landing Craft, Vehicle, Personnel (LCVPs) would transfer them to one of the four LSTs that had been converted into evacuation control centres, situated a mile offshore. Patients would receive emergency treatment and their details would be logged before they were transferred via another LCVP to one of the three hospital ships, the Samaritan, the Solace and the Bountiful. The auxiliary hospital ships Pinkney and Ozark were also available. Casualties would then be
shipped to Saipan and Guam, where 5000 beds were waiting. The plan was to evacuate the wounded directly from Iwo Jima as soon as transport planes could land on the island.
Training and Rehearsals
All three Marine divisions trained continuously throughout the winter of 1944/45. Troops practised loading and unloading from amphibious vehicles and landing craft. They also perfected the new tactics they would be expected to use on Iwo Jima, with the emphasis on how to silence bunkers and pillboxes.
Pole-charges, explosives strapped to a long handle, were effective for knocking out bunkers. The Marines had to work their way forward under covering fire until they were close enough to push the charge through the embrasure. (NARA-127-GW-112017)
Towards the end of November 1944 each division received around 2500 replacement drafts and although they had basic combat skills, it was too late to integrate them into the training programme. Instead they would be used to unload stores on the beaches and help move them inland. They would join units as soon as needed to replace casualties. The late delivery of DUKWs and new M4A3 Sherman tanks also caused problems.
Troops practised loading in the Hawaiian Islands over the Christmas and New Year period before they joined the Joint Expeditionary Force at Oahu in the Hawaiian Islands. Large rehearsals followed between 12 and 18 January, but the LSTs could not be beached because of underwater reefs, and the DUKWs stayed onboard because they were vulnerable to corrosion after spending time in seawater. Despite the problems, the Hawaiian exercises were valuable for everyone, particularly the inexperienced 5th Division.
Marines cross the forward well deck of their landing ship to take their place at the top of a cargo net. Their tiny landing craft are being lowered into the sea in the background. (NARA-127-GW-112470)
The final rehearsals were held in the Marianas Islands in mid February and while the Marines climbed aboard their landing craft, they did not land on the shore. Instead, the emphasis was on bringing together the different shipping and air elements. The manoeuvres allowed the Attack Force carrying the Marines (Task Force 53) to check communications and coordination with the armed landing craft of the Amphibious Support Force (Task Force 52) and the ships of the Naval Gunfire and Covering Force (Task Force 54). Once the training was over the combined elements of Fifth Fleet (Task Force 50) and Joint Expeditionary Force (Task Force 51) headed for Saipan.
Sailing to Iwo Jima
While 5th Division loaded at Hawaii, 4th Division loaded at Maui and 3rd Division loaded at Guam; corps and garrison troops loaded into six APAs and four AKAs in the Hawaiian area. Eventually, 485 ships were loaded and heading for Saipan to assemble as Task Force 51. There were 70,000 men and around 98,000 tons of cargo on board, the largest amphibious invasion assembled so far in the Pacific. The transport squadron carrying Task Force 51 was organised into three transport divisions, one for each of the Marine divisions. Each transport division allocated four troop transports known as Auxiliary Personnel, Attack (APAs) and one cargo ship known as Auxiliary Cargo, Attack (AKA) to a transport assault division which carried the divisional troops. It also allocated one APA and one AKA to carry corps troops and their supplies.
Landing Ship, Tanks (LSTs) and Landing Ship, Mediums (LSMs) carried the assault infantry and their amtracks, the artillery and their DUKWs, as well as tanks and other mechanised equipment. The assault troops were loaded in LVTs and carried to Iwo Jima in LSMs. 4th Division had sixteen, 5th Division had thirteen; two LSMs carried Corps troops. The planners had made sure that men, equipment and ammunition would be landed together ready to go straight into action. They also saw to it that the LSMs were loaded with spare water, ammunition, rations, fuel and lubricants so that the Marines were self sufficient until their supply chain was established.
Each division had nineteen LSTs and while 3rd Division had two extra to carry its tank battalion, four carried Corps troops. The LSTs were also preloaded with spare cargo. 50 amphibian cargo trailers were also loaded and sailed on LSV Ozark ready to go ashore on D-Day; the Ozark would then serve as an evacuation hospital.
The Landing Force convoy started arriving off Saipan on 14 February and the following afternoon it started heading north with an aircraft carrier and naval ships for protection. The transports carrying RCT 21 followed two days later so that it would ready off Iwo Jima by mid morning on D-Day. The transports carried 3rd Division and RCT 9. The Expeditionary Troops’ reserve followed over the next 48 hours; they would be in position 80 miles off the island by D-Day.
The Preliminary Bombardment
By 19 February 1945 Iwo Jima had already endured the longest and most intensive aerial attack delivered in the Pacific during the Second World War. It had started with a carrier raid in June 1944 and Seventh Air Force’s B-24 Liberator bombers stationed on the Marianas Islands began a six-month bombing campaign in August. The frequency and intensity of the air raids steadily increased and Marine B-25 medium bombers started their own raids in early December from new bases on the Marianas. Fighters also carried out low-level attacks, often targeting Japanese ships delivering troops and supplies to the island; 23 ships were sunk, leaving the garrison short of many essential items.
The Iwo Jima Air Support Plan began on D-20, by which time the Marianas-based Liberators were flying an average of 30 daily sorties over the island. V Amphibious Corps hoped that the intensive air raids would neutralise the Japanese airfield installations, knock out gun positions and destroy camouflage, uncovering new targets.
One point of contention between the Navy and the Marines was the duration of the preliminary naval gunfire bombardment. The original plan had a cruiser division opening the bombardment on D-8 while seven pre-Second World War battleships and six more cruisers would join in on D-3. The Marine naval gunfire specialists thought it would be insufficient based on their experiences on Tarawa, Saipan and Peleliu, where the assault troops had suffered heavy casualties on the beaches. They either wanted more ships or a longer bombardment to soften up the Japanese defences.
AIR SUPPORT
Support Carrier Group (Task Group 52.2) had eleven escort carriers: Sargent Bay, Natoma Bay, Wake Island, Petrof Bay, Steamer Bay, Makin Island, Lunga Point, Anzio, Bismarck Sea, Saginaw Bay and Rudyerd Bay. The Group’s planes carried out most of the close air support missions for the Marines until Airfield 1 was open on 8 March.
General Schmidt initially requested a ten-day bombardment by one cruiser division and three battleships but his request was denied. He reduced his request to nine days and then to four days but the naval planners insisted on only three days. Schmidt finally asked if the ships could concentrate their shelling on the landing beaches; he was turned down again.
While it appears that the Navy planners were being inflexible, they had a good reason based on the strategy they had chosen. Fast Carrier Force (Task Force 58) was scheduled to attack Tokyo at the same time as Task Force 51 approached Iwo Jima, forcing the Japanese Navy Air Service to protect the capital rather than attack V Amphibious Corps. If heavy seas or enemy action forced Task Force 58 to withdraw, the Japanese planes could head to Iwo Jima. The naval planners argued that the bombardment had to be kept to a minimum period to limit the chances of it being disrupted. The Navy was also concerned about the amount of ammunition its battleships and cruisers could carry. They would have to be resupplied if the bombardment lasted longer than three days, a dangerous activity in the middle of a battle.
By the end of January it was clear that several major support vessels would not be ready. Some were still needed in the Philippines, others were being repaired. It meant that the Navy commanders had to look for alternative ships while their planners issued a revised bombardment plan on 28 January. The new battleships North Carolina and Washington were allocated to the invasion force but while they had powerful 16-inch guns, they would not reach Iwo Jima until D-Day.
On 27 January, Admiral Spruance took over from Admiral William F. Halsey on Ulithi in the Caroline Islands and the US Third Fleet was renamed t
he Fifth Fleet. At the same time, Vice Admiral Marc A. Mitscher replaced Vice Admiral John S. McCain as commander of the Fast Carrier Force and it was renamed Task Force 58.
Task Forces 52 and 54 reached the Marianas on 12 February and two days later all the shore bombardment units headed for Iwo Jima. While Rear Admiral Bertram J. Rodgers’ Gunfire and Covering Force (Task Force 54) controlled the battleships and cruisers, Rear Admiral William H.P. Blandy’s Amphibious Support Force (Task Force 52) controlled the smaller vessels. Its Gunboat Support Units, Mortar Support Group and Rocket Support Group would target the beach defences while the Air Support Control Unit and Support Carrier Group would coordinate airstrikes. The Mine Group and Underwater Demolitions Group would carry out beach reconnaissance and destroy underwater obstacles.
On the morning of 16 February, Rear Admiral Rodgers’s Naval Gunfire and Covering Force (Task Force 54) began shelling Iwo Jima. Admiral Blandy’s staff on board the Estes (AGC 12) controlled the bombardment and its target priorities were as follows:
Priority A Coastal guns and anti-aircraft guns which threatened ships and aircraft
Priority B Bunkers and pillboxes threatening the Landing Force
Priority C Caves, bivouac areas, ammunition and fuel dumps
The Task Force had three days to neutralise 724 A and B targets. It was a tall order for the 6 battleships, 4 heavy cruisers and 1 light cruiser.
Rear Admiral Alexander Sharp’s Mine Sweeping Group (Task Group 52.3) led Task Force 54 to its firing positions and although they were ready to open fire at 08:00, intermittent low clouds blinded the airborne observers. Firing schedules had to be abandoned and the ships’ guns only fired when there was a break in the clouds. To make matters worse, anti-aircraft fire forced observation planes to stay above 3000 feet so they could not assess the effects of the bombardment. By the end of the first day it was clear that the naval bombardment had achieved little. The overcast skies also prevented Army Air Force bombers from flying over Iwo Jima, although the planes belonging to Rear Admiral Calvin T. Durgin’s Support Carrier Group (Task Group 52.2) had flown 158 sorties.