The Invasion of Saipan, Tinian and Guam
June 1944 would find the US Navy involved in two of the most ambitious naval expeditions ever attempted and on opposite sides of the globe. Even as Operation Overlord returned the Allies to France, Operation Forager was about to deliver the Marines and Army onto the Marianas Islands.
The Marianas were considered important for several reasons. The first was the Chief of Naval Operations, Admiral Ernest King’s conviction that the Marianas were the key to the Central Pacific because they dominated the communications with Japan’s "Inner South Seas Empire”. Capture of the islands would provide the Pacific Fleet with bases from which they could attack the enemy’s air-sea communications and strike with equal ease at Palau, the Philippines, Formosa or China. Navy planners also felt that a bold strike into the vitals of the Japanese position would force the Combined Fleet to give battle and hazard itself to destruction at the hands of US Navy.
The Army Air Corps also had an equally important need for bases from which its new long range bomber, the B-29, could make non-stop strategic strikes on the Japanese home islands.
The Marianas Islands consist largely of rugged wooded mountains (though this is somewhat less true of Tinian) and are quite large compared with Tarawa. Guam is more than 30 miles long, Saipan about 14. They are ringed with coral reefs which compound the difficulties of amphibious assault by channelizing the approach to the beaches. The Japanese defenders by mid-1944 numbered some 60,000, about half of them on Saipan. Situated more than a thousand miles from the nearest US base, this enemy force represented the most remote and formidable target the Navy/Marine team had so far attempted. The Navy would find its logistical capabilities stretched to the limit to support the largest amphibious operation yet mounted in the Pacific.
US intelligence estimated the Japanese force on Saipan at 19,000. In fact there were more than 29,000. Three quarters of this number were Army including the 43rd Infantry Division, 47th Independent Mixed Brigade, (essentially a regimental combat team with extra artillery), a tank regiment, two engineer regiments, an antiaircraft regiment and other smaller units. These troops were commanded by General Y. Saito The Navy made up the rest of the forces. They were commanded by Admiral Nagumo of Pearl Harbor fame. The Navy was concentrated around Tanapag Harbor, were well fortified and manned a variety of heavy artillery including a battery of 8 inch guns. There were also three airfields on Saipan but their planes had long been destroyed by the 5th Fleet’s fighters.
Admiral Raymond Spruance’s 5th Fleet, some 800 ships, was charged with transporting 80,000 Marines and nearly 50,000 soldiers to the landing beaches. They would be escorted by Task Force 58, Admiral Marc Mitscher’s superb force of 12 fast aircraft carriers flying some 800 aircraft and accompanied by 8 battleships and 80 other warships. TF 58 was the weapon with which the US Navy planned to destroy the Japanese Combined Fleet when and if it ventured forth to support the Marianas garrisons.
The Expeditionary Troops comprising 3 Marine Divisions, a reinforced Marine Brigade and 2 Army Infantry Divisions were commanded by Lt General Holland M. Smith, USMC. This force was divided into the Northern Troops and Landing Force, for the assault of Saipan and Tinian, commanded directly by General Smith, and the Southern Troops and Landing Force, for the following operation against Guam, commanded by Maj. General Roy Geiger, USMC.
Attack on Saipan
After intense air operations on the 11th and 12th of June, followed on the 13th by a daylong bombardment from the fast battleships of TF 58, the plan called for the 2nd and 4th Marine Divisions to land abreast on about four miles of beaches on the west side of Saipan south of Garapan, the 2nd on the left and the 4th on the right. In reserve would be the 27th Infantry Division part of which had fought at Makin and Eniwetok. To the north above Tanapag units of this floating reserve would stage a demonstration to draw Japanese attention away from the real landings. The immediate objective of the landings was to seize a line far enough inland to preclude Japanese direct fire on the beaches. To do this rapidly over 700 amphibian tractors, some armored models mounting a 75mm infantry gun, had the job of pushing the first waves about a mile inland before debarking. This was a bold plan but it would come up short in execution.
As June 15th dawned bright and clear, a specially trained bombardment squadron consisting of 4 old but effective battleships, 8 cruisers and 7 destroyers moved close aboard the Charen Kanoa beaches and commenced firing. The Marines came on four regiments abreast led by the armored amphibians. Preceding them were 24 rocket firing LCI-gunboats. Overhead, Marine and Navy fliers dropped bombs and made strafing runs on suspected enemy strongpoints. A thick pall of smoke and dust obscured the low ridges which rose in the rear of the beaches. Battleship Tennessee fired her big guns point blank at the fortifications on Agingan Point that flanked the 4th Division’s landing beaches. Everything that could be done had been done. Admiral Turner signaled the traditional order to "Land the landing force” In waves the Marines went in. As the first LVTs clambered over the coral reef they seemed to explode under a torrent of Japanese shells. The Japanese had positioned colored flags in the lagoon to mark the range of the landing forces and now heavy artillery and mortar fire rained down on them with pin-point accuracy. Out of the 68 armored amphibians which had led the 6th and 8th Marine Regiments to the beach, 31 were destroyed or disabled. While the leading waves landed and debarked far short of the plan, the Japanese opened an accurate long range grazing fire with heavy machine guns sited in the hills around. Far from being suppressed by the prelanding bombardment, they had survived with most of their artillery and fortifications intact. The Marines found themselves being pounded by heavy guns firing from defillade while taking continuous flanking fire from Agingan and Afetna Points. Losses among officers was very high. 2nd Battalion, 6th Marines, had four different commanders before nightfall. Over 2,000 casualties were sustained during the landing.
The next two days, June 16 and 17, were spent struggling to expand the beachhead enough to prevent the Japanese from observing and taking every move of the Landing Forces under fire. The 2nd Marine Division had tough going as it fought to gain the slopes of Mounts Tapotchau and Tipo Pale. On the night of the 15th, the 8th Marines repelled a strong counterattack while the next night, B Company, 6th Marines, were overrun by the first large scale tank attack faced by Marines during the war. Morning light would reveal the derelict hulks of 31 destroyed tanks inside B Company’s wire.
Meanwhile developments at sea had taken a fortuitous turn for Admiral Spruance. The Japanese Fleet was coming out. It was decided to delay the landings on Guam and to land the Army’s 27th Infantry Division on Saipan immediately. After night fell on June 17th, Spruance and the 5th Fleet sortied to meet the Japanese in a battle later known as "The Marianas Turkey Shoot”.
Although the fleet and most of the naval gunfire was absent, conditions were improving onshore. Gen. Holland Smith had landed and set up his headquarters at Charan Kanoa. With the arrival of the 27th Division, all of the Northern Landing Force were ashore. After fierce resistance the Japanese were beginning to feel the constant pressure the Marines were exerting. On the night of June 18th, Saito ordered his secret papers and codebooks destroyed and sent a message to Tokyo: "By becoming the bulwark of the Pacific with 10,000 deaths we hope to requite the Imperial favor.” That day the Marines pushed across the cane fields towards Magicienne Bay on Saipan’s east side. On the right of the 4th Marine Division, the 165th Infantry secured Aslito airfield with no opposition. By the 20th, the island was bisected when the 4th Marine Division reached the sea on the opposite side of the island.
While the Marine Divisions formed line abreast to drive north to the end of the island, Spruance’s 5th Fleet was scoring a huge victory with the destruction of Japanese naval aviation in the Battle of the Philippine Sea. Spruance comes in for criticism from some quarters for not chasing Ozawa’s battered force as they withdrew but the Marines were glad to see the return of the fleet and its big guns.
The terrain of the north end of Saipan was described by one officer as "a nightmare of sheer cliffs and precipitous hills,". The fighting was characterized by the use of the flame-thrower, satchel charge, grenade and bulldozer. Suicidal charges by the trapped Japanese led to many episodes of hand-to-hand combat.
While the Japanese refused the opportunity to surrender and suffered nearly total casualties in every encounter with the Marines, Corporal John Basilone, a Japanese speaking Marine from Los Angeles was successful in talking nearly a 1,000 Japanese into surrendering and thus saving their lives. For this Basilone was awarded the Congressional Medal of Honor, his country's highest military award.
On June 22nd, the 27th Infantry Division was inserted into the center of the line between the two Marine divisions. Unfortunately the Army regiments were unable to maintain pace with the battle-hardened Marines on their flanks and soon the line took on a concave U shape. By the end of the day General Holland Smith could no longer hide his concern over the poor showing of the 27th Infantry Division. Major General Sanderford Jarman, USA, senior army officer on Saipan was asked by General Smith to go to the commander of the 27th, General Ralph Smith, USA, and impress upon him the need for haste. Jarman found Smith despondent over his division’s lack of fight and quoted him as saying if the division did not do better on the morrow that he (General Smith) should be relieved. Unfortunately this came to pass the next afternoon when Holland Smith exercised his prerogative and replaced him with the aforesaid General Jarman. This episode would create much bitter inter-service rivalry between the Marines and the Army that would have repercussions later on in the war. While the 27th Division tried to work out its command problems, the 2nd Marine Division in a bold attack captured Mount Tapochau. This was the beginning of the end for the Japanese. On July 1st the battle for Saipan entered its final stage. The 2nd Division over three days of sustained fighting captured the shattered ruins of Garapan and Tanapag Harbor.
As the remaining defenders were compressed into an ever smaller area, General Holland Smith became concerned about the possibility of a final banzai charge and on July 2nd he paid a visit to the headquarters of the 27th Infantry Division to warn them to expect such an attack that night. At 0445 the next morning 2,500 ragged Japanese soldiers, short of weapons, ammunition and food surged down upon the 105th Infantry Regiment. Despite the warnings a gap of 500 yards separated two of the Regiment’s battalions and it was here that the weight of the attack fell. In a fight only too reminiscent of Custer’s Last Stand, a battalion commander was killed in his command post manning a .30 cal. machine-gun to the last. During this ordeal the regiment’s third battalion posted nearby, stayed put and took no part in the fight. In the rear of the 105th Infantry the attack swept into the 3rd Battalion, 10th Marines. Here the marine gunners cut the fuzes down to muzzle burst and fired their 105s point blank into the enraged enemy. The attack finally ended in a hand-to-hand fight among the fox holes of the 10th Marines. The artillery battalion suffered the loss of 136 men including the commander, killed at his guns. The two army battalions suffered a loss of 668 casualties and were evacuated the next day.
Before the final banzai attack, General Saito, too ill to take part, gathered his staff for a farewell feast of sake and canned crab meat which ended with the General’s ritual suicide. A day later in a cave not far from the scene of Saito’s death, Admiral Nagumo, who had launched the attack on Pearl Harbor, took his life.
Although the island was declared secure on July 9th, some Japanese would hold out like shadows for months to come. The final mop up operations would see some of the most pathetic scenes of the Pacific War as Japanese civilians choose to leap to their deaths from the crags of Marpi Point rather than surrender to the Marines who were powerless to stop them.
Saipan cost the United States 16,525 casualties including 3,426 killed in action but it provided the first B-29 base in the Pacific. Japanese losses were over 29,000. A Japanese Admiral said, "Our war was lost with the loss of Saipan. I feel it was a decisive battle." General Holland Smith considered Saipan the decisive battle of the Pacific offensives.