Strikes on the Marianas

On 12 June 1944 aircraft from fifteen American carriers spent the whole day bombing and strafing airfields, harbours and gun batteries on Saipan, Tinian, Guam, Rota and Pagan. It was the first full day of preparation for Operation Forager – the invasion of the Marianas and the largest American amphibious operation in the Pacific up to that time. The next day fast battleships closed Saipan and began shelling the coast, and on 14 June the old fire-support battleships took their place. On the other side of the Pacific the Japanese naval command realised that this time it faced not another raid but an invasion, and began gathering its ships for the “decisive battle”.

War chronologies describe these days in a few sentences: the fleet carrying the invasion troops left Pearl Harbor on 5 June, the carriers began their strikes on the Marianas on 12 June, the warships began shelling Saipan on 13 June, and Admiral Soemu Toyoda responded by ordering the fleet to attack the Americans. These statements need refining. According to the American official history (Philip A. Crowl, Campaign in the Marianas), the tank landing ships (LSTs) carrying the Marine assault units left Pearl Harbor as early as 25 May, the transports on 29 and 30 May, and the ships carrying the reserve 27th Infantry Division between 25 May and 1 June; by 5 June, therefore, the convoys had already been at sea for several days, heading for the staging bases at the atolls of Enewetak and Kwajalein. The first carrier strike came on the afternoon of 11 June, a day earlier than planned. The shelling from the sea did indeed begin on 13 June, but on that day Toyoda merely declared “readiness for the decisive battle” under Plan A-Go; he gave the order to begin the operation on 15 June, the day of the landing on Saipan.

Why the Marianas

The Marianas lie roughly halfway between New Guinea and Japan. Saipan, Tinian and Rota had belonged to Japan since the First World War as a League of Nations mandate, and the Japanese had seized American Guam in December 1941. Admiral Ernest King, the commander of the US Fleet, had argued since 1943 that taking the archipelago would cut Japan’s lines of communication with the Caroline Islands and Palau and force the Japanese fleet to give battle. He was backed by General Henry Arnold, the commander of the Army Air Forces, who was looking for airfields for the new long-range bomber, the Boeing B-29 Superfortress. Saipan and Tinian are about 2,400 kilometres from Tokyo – within range of a B-29 with a full bomb load. No other place the Americans could realistically take in 1944 offered such an opportunity to strike Japanese cities and industry.

The pace of the war in the Central Pacific quickened in the first months of 1944. At the beginning of February the Americans took Kwajalein, on 17 February they landed on Enewetak, and a carrier raid on Truk showed that the notorious base was no impregnable fortress. On 23 February Mitscher’s aircraft attacked the Marianas for the first time and photographed their coasts. On 12 March the American Joint Chiefs of Staff set the invasion of the Marianas for 15 June, and a day later Admiral Chester Nimitz gave the operation top priority. Truk was to be bypassed; at the end of April the carriers struck it a second time so that it could not threaten the invasion.

The operation as a whole was directed by Admiral Raymond Spruance, commander of the Fifth Fleet. The amphibious forces (Task Force 51) were commanded by Vice Admiral Richmond Kelly Turner, who also personally led the Northern Attack Force, assigned to Saipan and Tinian. The ground troops came under the Marine General Holland Smith. The V Amphibious Corps was to land on Saipan: the 2nd and 4th Marine Divisions, with the Army’s 27th Infantry Division in reserve. Rear Admiral Richard Conolly’s Southern Attack Force, with the 3rd Marine Division and the 1st Provisional Marine Brigade, was to take Guam. According to the most frequently cited figures, about 535 warships and other vessels and more than 127,000 troops took part in the operation – all in the same week in which, on the other side of the world, the Allies were landing in Normandy.

Convoys under way

The troops for Saipan embarked in Hawaii, where amphibious exercises were held in May. On 21 May, in West Loch at Pearl Harbor, an ammunition explosion aboard one of the landing ships started a fire that destroyed six LSTs; more than 160 men were killed, mostly sailors and Marines. The losses were quickly made good and the timetable did not suffer. The slow LSTs, each carrying more than three hundred Marines and the amphibious tractors of the first assault waves, left Pearl Harbor on 25 May, the transports on 29 and 30 May. The ships bound for Saipan assembled in the lagoon at Enewetak, where some of the troops were transferred from the transports to the LSTs and the staff received the last aerial photographs of the island. The convoys carrying the reserve 27th Division assembled at Kwajalein, while the forces destined for Guam came from the Solomon Islands. By 11 June the last transports had left Enewetak and four convoy groups were steaming west.

The carriers went ahead of them. On 6 June – the day of the Normandy landings in Europe – Vice Admiral Marc Mitscher’s fast carrier force (Task Force 58) sailed from Majuro atoll: seven large carriers, eight light carriers, seven fast battleships, three heavy and ten light cruisers and 52 destroyers, divided into four task groups. Their job was to destroy Japanese air power in the Marianas, shield the convoys from the Japanese fleet and, from 13 June, also destroy the fortifications on the islands.

The carrier strike

The plan called for the first attack at dawn on 12 June, three days before the landing. The weather, however, was good, the refuelling of the destroyers went more smoothly than expected and the carriers came within range of the islands early. Mitscher asked Spruance for permission to attack on the afternoon of 11 June. He argued that every previous Task Force 58 strike had begun at dawn and a change of pattern would catch the enemy off guard. Spruance agreed. At 1 p.m., about 200 nautical miles north-east of Guam, 225 aircraft took off, mostly Grumman F6F Hellcat fighters. The Americans lost twelve machines. Japanese losses were put at 147–215 aircraft destroyed or badly damaged – these are American figures and must be treated with caution, but Nimitz later judged that “air superiority was secured by the first fighter attack of 11 June”. From then on Japanese land-based aviation in the Marianas was no more than a minor nuisance.

A Japanese tank crewman on Saipan wrote in his diary that “for about two hours the enemy planes ran amok” while the defenders could only look on helplessly. Yet the command on the island still did not understand what was happening. As late as the afternoon of 11 June the 43rd Division staff ordered the construction of a new road inland between the Marpi and Aslito airfields – a long-term project that drew men and materials away from fortifying the beaches. The Japanese took the attack for another raid like the one in February.

12 and 13 June

For the next three days, from 12 to 14 June, all four of Mitscher’s groups sent waves of aircraft over Saipan, Tinian, Guam, Rota and Pagan according to plan. The aim was to finish off Japanese air power, put the airfields out of action and destroy the coastal and anti-aircraft batteries. Japanese records indicate that most of the damage was done by bomb splinters and blast – command posts were wrecked and some guns damaged.

On 12 June the American airmen came upon unexpected prey. Some 125 miles west of Pagan they spotted a northbound convoy of about twenty vessels trying to escape from the threatened area. According to post-war findings they sank nine merchant ships totalling almost 30,000 tons and several escorts, including a large torpedo boat and three submarine chasers. The same day aircraft sank a ship off the north-west coast of Saipan and another in Tanapag harbour, while a third, damaged, had to beach itself. On 13 June aircraft from Rear Admiral Joseph J. Clark’s group attacked another convoy fleeing south along the west coast of Guam.

On 13 June the bombardment from the sea began. Seven fast battleships and eleven destroyers under Vice Admiral Willis Lee were detached from the carrier screen. From 10.40 a.m. until about 5.25 p.m. they shelled the west coasts of Saipan and Tinian, while ten fast minesweepers swept the waters off the beaches, finding no mines and meeting no fire from the shore. At night the battleships withdrew and five destroyers kept up harassing fire. The results of the first day’s shelling were doubtful. The Japanese 31st Army staff reported that the streets of Garapan and Charan Kanoa had been all but levelled, but that casualties were light. Holland Smith’s naval gunfire officers were sceptical: the crews of the fast battleships had not been trained to bombard land targets, the airmen spotting the fall of shot could not pick out targets on the ground, and for fear of mines the ships could not come closer than 10,000 yards (about 9 kilometres) from the shore.

On the morning of 14 June Rear Admiral Jesse Oldendorf arrived off Saipan with two fire-support groups – seven old battleships, eleven cruisers and 26 destroyers. Some of those battleships had survived the attack on Pearl Harbor. All day they shelled the coast from closer range, and under their cover frogmen of the underwater demolition teams (UDTs) surveyed the reefs and the approaches to the beaches. The Japanese no longer had any doubts: the 31st Army staff reported that the enemy was examining the reefs from small boats and marking passages for tanks, and predicted that the landing would come that night or at dawn.

The defenders

The Japanese had known since February that the Marianas would be the next target and had been hurriedly reinforcing the garrisons. Ground forces in the archipelago were commanded by the 31st Army under General Hideyoshi Obata, who was on Palau when the invasion came and could not get back. On Saipan the effective commander was General Yoshitsugu Saitō, commander of the 43rd Division, which had reached the island only in May and early June. Some of the transports carrying reinforcements were sunk on the way by American submarines; the survivors were put ashore on Saipan, often without weapons or equipment. According to Crowl there were about 25,500 army troops and about 6,200 naval personnel on the island. Saipan was also the headquarters of the Central Pacific Area Fleet under Vice Admiral Chūichi Nagumo, the commander at Pearl Harbor and Midway. The fortifications were unfinished: cement and materials were in short supply, and many guns had still not been emplaced. Japanese land-based aviation in the Marianas, under Vice Admiral Kakuji Kakuta’s First Air Fleet, had already been weakened by the transfer of some of its aircraft to the fighting for Biak.

Plan A-Go and Toyoda’s orders

At the beginning of May Admiral Soemu Toyoda took command of the Combined Fleet, succeeding Admiral Mineichi Koga, who had been killed at the end of March. His Plan A-Go envisaged a single decisive battle with the American fleet, preferably in the area of Palau and the western Carolines, where Japanese ships could be supported by land-based aircraft and the tankers were close at hand. The main body of the fleet – Vice Admiral Jisaburō Ozawa’s First Mobile Fleet with nine carriers – waited at the Tawi-Tawi anchorage in the southern Philippines, close to the oil of Borneo. When the Americans landed on Biak on 27 May, the Japanese saw it as a threat to the plan and launched Operation Kon – an attempt to ship reinforcements to the island. For this they moved part of their aircraft and ships south, including the super-battleships Yamato and Musashi under Vice Admiral Matome Ugaki, which assembled off Halmahera for the third attempt to break through to Biak.

The strikes on the Marianas settled the matter. As early as 11 June the Combined Fleet staff concluded that the Americans had come to take the archipelago, and recalled the aircraft previously sent south. The Naval General Staff in Tokyo was more cautious: it believed this was merely a carrier raid and feared using up its scarce fuel. Nevertheless, on 13 June Toyoda declared “readiness for the decisive battle” under Plan A-Go and called off Operation Kon. That same day Ozawa’s fleet left Tawi-Tawi for the Guimaras anchorage in the central Philippines, and Ugaki’s force was ordered to join it. Toyoda formally set Operation A-Go in motion on 15 June, when the Marines were already landing on the beaches of Saipan; according to the widely cited account, his order echoed Admiral Tōgō’s signal at Tsushima in 1905 – “the fate of the Empire rests upon this one battle”.

Place in the war

The strikes of 11–14 June gave the Americans what they needed before the landing: command of the air over the Marianas and reconnaissance of the beaches. They did not, however, destroy most of the Japanese guns and positions inland on Saipan – as the Marines discovered when they landed near Charan Kanoa on 15 June under heavy artillery fire. Four days later Ozawa’s fleet attacked Task Force 58 west of the Marianas. In the Battle of the Philippine Sea on 19–20 June Japanese carrier aviation suffered a defeat from which it never recovered, and the Japanese lost three carriers. Plan A-Go, designed to destroy the American fleet, ended with the loss of what remained of Japan’s carrier strength.

Saipan fell on 9 July after three weeks of heavy fighting in which almost the entire Japanese garrison was killed, along with many civilians; in the last days hundreds of them – by some estimates more than a thousand – leapt from the cliffs in the north of the island or killed themselves with grenades, often under pressure from Japanese soldiers. In the wake of this defeat the cabinet of Prime Minister Hideki Tōjō resigned on 18 July; the fall of Saipan also convinced Emperor Hirohito’s circle that the war could not be won. In the battles for the Mariana Islands the Americans landed on Guam on 21 July and on Tinian on 24 July. Large airfields were built on the captured islands. On 24 November 1944 B-29s from Saipan attacked Tokyo for the first time, and in 1945 the Marianas were the starting point for the raids that burned out most of Japan’s large cities. In August 1945 the aircraft that dropped the atomic bombs on Hiroshima and Nagasaki took off from Tinian.