SAIPAN

by Brian D. Blodgett

At the Washington Planning Conference in February and March of 1944, the planners for the Pacific Campaign decided that the primary objective for the near future was to establish a base in the area of Luzon, Formosa, and the Chinese Coast. They believed that from this base, vital lines of communications from Japan to the Netherlands Indies could be severed. They also believed that bases in this area could be used by long range bombers (B-29s) to attack the Japanese home islands. The planners further believed that if an invasion of Japan was to occur that these bases could be used as staging areas for the vast number of troops that would be required.

While both General Douglas MacArthur (USA) and Admiral Chester Nimitz (USN) submitted their own plans to achieve the goal of the Washington Planners, neither one fully met the needs of the Joint Chiefs of Staff (JCS). The JCS realized that they had to balance the needs of both Nimitz and MacArthur and issue an order to both Commanders in Chief (CinCs). To Nimitz they directed that his forces control the Marianas-Carolines-Palau Islands. The purpose of this paper is to examine the United States conquest of one of these islands - Saipan.

Saipan is the northern most of the southern four islands in the Marianas chain. The other three, from north to south, are Tinian, Rota, and Guam. In total, the Marianas are comprised of fifteen volcanic islands that run in a generally north-south direction from 20^o32'N 144^o54'E to 13^o15'N 144^o43'E. Saipan is located about 1,200 miles from Tokyo, 1,500 mile from Manila, and over 3,200 miles from Pearl Harbor. The island has two main seasons, a dry season from November to March, and a wet season from April to October. During the dry season the winds are usually from the north and east and by August the winds have changed direction and are from the southwest. Cloud cover is abnormally high with the island being obscure roughly 70% of the time. The climate is generally mild with the yearly temperature ranging from 72^o F to 85^o F. During the wet season, August being the wettest month, showers may last for only a few minutes to over 2 hours. During the wet season around 85 inches of precipitation usually falls on the island.

The north, east, and south ends of the island are generally comprised of steep slopes with narrow beaches that quickly give way to deep water. The western shore of the island has more gentle slopes with the beaches being protected by outlying reefs. Exception to this barrier reef exists near the small town of Chalan Kanoa. A dredged channel leading into Tanapag Harbor also exists. This harbor offers protection from heavy winds and high seas from almost all directions. The other natural harbors on the island only offer limited protection, depending on the direction of the wind.

Saipan's most dominating feature is Mount Tapotchau, which is located near the center of the island and is 1,554 feet high. A ridge runs northward to Mount Marpi (832 ft) at the northern end of the island. East of the ridge the terrain ends abruptly at the steep coastal cliffs, but to the east the terrain slopes gently down to the beaches. The southern section of the island is comprised of a plateau that has Mount Tapotchau to the north and Mount Kagman to the southeast and Mount Nafutan to the south. The island is only 85 square miles in size. In 1944, 70% of Saipan was covered with sugar cane cultivation. A marsh is located near Chalan Kanoa.

Saipan combined everything that the Americans had learned to hate about fighting the Japanese. The island was comprised of varied landmasses with swamps, sugarcane fields, jungle-covered mountains, and steep ravines. The island was protected by either deep water and steep slopes and cliffs, or coral reefs protecting an interior shallow lagoon. The island also had plenty of caves that the Japanese could use as bunkers or for artillery positions.

Due to the unique physical features of the island, the best point for an invasion was on the western side near the town of Chalan Kanoa and south of Garapan. Since the Marianas had to be occupied by during the summer months to facilitate the continued major offensive against Japan, Nimitz was ordered to occupy the Southern Marianas by 15 June 1944. Although this was during the wet season, it was prior to August and would allow the invading forces more time to conquer the islands before the heavy rains arrived.

Although Nimitz was the overall commander in chief of the Central Pacific Areas, he entrusted Vice Admiral Raymond A Spruance (USN), the commander of the Fifth Fleet, to conduct the invasion of the Marianas. Spruance, in turn,. ordered the Joint Expeditionary Force (Task Force 51) to invade the Marianas. Task Force 51 was under the command of Vice Admiral Richmond Kelly Turner (USN). The attack on the Marianas was divided into two forces, the Northern Attack Force (also known as Task Force 52 and under the command of Turner) which was the amphibious units that were to conduct the attack on Saipan. The tactical commander of the troops once ashore (Task Force 56, also known as the V Amphibious Corps) was to fall under Lieutenant General Holland M. Smith (USMC). Smith was well suited for this position as he had supervised both the 1^st Infantry Division and the 1^st Marine Division through basic landing problems on the East Coast prior to his transfer to the Pacific Theater. Smith had also been in command of the assault forces of Tarawa, Makin, Kwajalein, and Eniwetok. Nimitz was the overall commander of the mission, but the tactical commanders of the Saipan invasion were Turner and H. Smith. Under arrangements made between the Navy and Marine Corps, Turner would remain the tactical commander until H. Smith established his command ashore and it was determined that the burden of command could be transferred ashore.

The invasion forces under H. Smith were the 2^nd Marine Division, commanded by Major General Thomas E. Watson (USMC), the 4^th Marine Division, commanded by Major General Harry Schmidt (USMC), the 27^th Infantry Division, commanded by Major General Ralph C. Smith (USA), and the XXIV Corps Artillery, commanded by Brigadier General Arthur M Harper (USA). The 2^nd Marine Division had already seen action on Guadalcanal (one regiment) and at Tarawa (over 3,000 casualties). The 4^th Marine Division had participated in the invasion of the Kwajalein Atoll. The 27^th Infantry Division was a New York National Guard unit and was called into federal service in October of 1940. It was the first National Guard division to enter the Pacific War. It's first year and a half outside of the United States it served as the base defense force in the Hawaiian Islands. Elements of the unit saw action at Makin, Tarawa, and on the Eniwetok Atoll. The XXIV Corps Artillery unit had one battalion participate at Kwajalein, but the rest of the unit had not yet been exposed to combat.

On Saipan, the Japanese had been working on the island defenses since 1934 and by 1940 they had spent over the equivalent of over 7 million American dollars on air installations, fortifications barracks, ammunition storage areas, and other miscellaneous projects. Asilto airfield, located on the southern end of the island, was the principle air base in the Marianas. Tanapag Harbor also served as a seaplane base as well as a naval base. Although the Japanese, prior to the outbreak of the war, claimed that the construction was peaceful in nature, its twelve lighthouses on the islands each had a barracks, ammunition storage facilities, a command post, and a lookout station. By September 1941, Japan had set up radio direction finders and built additional storehouses, torpedo storage facilities, air raid shelters, as well as gun positions. All in the name of peace!

After Pearl Harbor, Saipan served mainly as a supply and staging area for troops, planes, and ships. The actual combat strength on the island was generally low (1,139 men in May 1943 and 1,437 men in February 1945). However, after the capture of Tarawa and Makin in the Gilberts, the Japanese knew that eventually American forces might attack Saipan. With this knowledge came an increased emphasis on the defense of the islands. The command of the Marianas, which used to fall under 4^th Fleet, was transferred to 31^st Army. Yet, in true Japanese form, a clear-cut command of the naval and army forces in the area was not established. Traditionally the navy and army did not have joint command relationships. They usually would discuss items of interest and agree on a common principle, but no overall commander oversaw the action of both forces. This practice held true in the Marianas. The 31^st Army was actually subordinate to the Central Pacific Area Fleet and the senior army officers resented being under the control of a naval commander. After much bickering, on 15 March 1944 a compromise was reached between the Army and the Navy. The senior officer present would command each island, be he navy or army. Furthermore, both the Central Pacific Area Fleet and the 31^st Army agreed that neither would assume complete responsibility over all of the islands!

This lack of a single command was made worse by the fact that all of the services actually had to rely on each other. The air forces in the area belonged to the navy but were supported by airbases generally under the control of the army. Army personnel had to reach the islands via naval transport. The high level of mutual dependency was made worse by the lack of a single unified commander. The movement of troops nto the 31^st Army area during 1944 complicated the issue of command even more. By May 1944, Japan had five divisions, six independent brigades, and five independent regiments in the Marianas area. Additionally, Japan had other independent units of battalion-sized units and below in the area that had been detached from their parent divisions and sent into the Central Pacific Area, three of these units were sent to the Marianas.

Lieutenant General Hideyoshi Obata, the commander of the 31^st Army, was headquartered on Saipan with his staff of 1,100 men. However, while Obata was in charge of the 31^st Army, General Saito commanded the troops on Saipan. Saito's largest organized unit was the 43^rd Division, composed of the 118^th, 135^th, and 136^th infantry regiments. The division's strength was nearly 13,000 men. Also on the island was the 47^th Independent Mixed Brigade, commanded by Colonel Yoshiro Oka. The strength of this unit was around 2,600 men and it had twenty-two artillery pieces. There were also a significant number of smaller units stationed on Saipan, along with units that were stranded there due to American submarine activity near the island. Amongst these were the 3^rd Independent Mountain Artillery Regiment (24 mountain guns), and the 9^th Tank Regiment (36 medium and 12 light tanks). The total number of soldiers on Saipan on 15 June was around 25,000 men. There were also slightly over 6,000 sailors of the 5^th Base Force on the island.

Saipan was divided into four sectors for defensive measures. The 135^th Infantry Regiment defended the North Sector of Saipan. Along the west, in the Naval Sector near Tanapag Harbor and Garapan, were the naval forces and one battalion of the 136^th Infantry Regiment. South of the Naval Sector was the Central Sector with only a battalion (+) of the 136^th Infantry Regiment. The South Sector actually extended from the southern most point on Saipan northward to the Central Sector and up the entire east coast of the island to the North Sector. This sector, which comprised nearly half of the island, held the 47^th Independent Mixed Bde, the 9^th Tank Regiment, the 3^rd Independent Mountain Artillery and the 25^th Antiaircraft Artillery Regiment (near Aslito airfield). The amount of forces in these sectors was determined by the likelihood of the United States conducting an amphibious invasion in the area. Due to the steep slopes, deep water, and cliffs around most of the island, the best and the most likely location for an amphibious assault was on the western side near Chalan Kanoa, south of Garapan. The Japanese doctrine, which was based on its previous defense of atolls, was to severely limit reserve forces and defend the beaches. With this in mind, the Japanese reserve force was composed of two companies of the 136^th Infantry Regiment and two companies of the 9^th Independent Mixed Brigade. All of these companies were located north of Magicienne Bay. Also in this area was the 9^th Tank Regiment whose mission was to counterattack any landings near Garapan or Tanapag. If landings would have taken place near Magicienne Bay then the tanks would counterattack into these areas.

The army artillery was located along the ridge and able to fire on both the western and eastern coasts. The artillery positions were carefully registered on the beaches and the waters offshore prior to the assault. In fact, small bamboo poles were stuck in the water off of the western beaches to assist the artillerymen in their targeting efforts. The navy had also created an extensive coastal defense plan with 12-cm, 14-cm, and 15-cm guns. The naval plan was to have seven batteries cover the western coasts, five batteries to cover the south and southeastern coasts, and four batteries to cover the northern beaches. Six additional batteries were also included in the overall naval defense plan; two to cover Aslito airfield, two to cover the center of the island, and a battery at both Tanapag and Marpi Point. While not all of these positions were ready when the invasion occurred, at least some of them were equipped and manned.

Along the ridges and hills overlooking the western beaches and the southern part of the island were three batteries of the 25^th Antiaircraft Regiment. Each of these batteries were low on ammunition and probably only had 5,000 rounds between them, instead of a planned 15,000 rounds.

By February 1944, the United States Navy had increased its submarine patrols in the vicinity of the Marianas and the approaches to the island chain. The submarines not only destroyed several troop transports that were bound for the Central Pacific area, but forced other transports to be stranded on Saipan. The 9^th Expeditionary Brigade and the 47 Independent Mixed Brigade were two of these units. These units were not properly equipped and therefore not fully combat capable since they were not originally scheduled to be stationed on Saipan and much of their equipment had been sunk by United States submarines.

A convoy carrying 7,000 men of the 43^rd Division was subjected to submarine attacks and five out of the seven transport ships were sunk. Fortunately, about 80% of the troops were saved, but when they arrived at Saipan they were generally without any equipment since it had gone down with the transports. The 118^th Infantry Regiment lost about 850 men and was so disorganized that it was considered to be combat ineffective. While it appears at first that Japan had adequate forces on Saipan to defend it, the truth is far from that. The 43r^d Division did not arrive on Saipan until early June and had very little time to prepare for the invasion. The two engineer units on Saipan who were responsible for the permanent fortifications had only arrived in April! The fact that the troops arrived without any order, missing equipment, and building materials (that were also lost to the submarine attacks) meant that the Japanese were not as well fortified on Saipan as their numbers indicated.

On 31 May, the 31^st Army Chief of Staff stated that:

"We cannot strengthen the fortifications appreciably now unless we can get materials suitable for permanent construction. Specifically, unless the units are supplied with cement, steel reinforcements for cement, barbed wire, lumber, etc., which cannot be obtained in these islands, no matter how many soldiers there are they can do nothing in regard to fortifications but sit around with their arms folded, and the situation is unbearable."

The failure of the Japanese to fortify Saipan forced them to rely on the 'hold the beach' tactic that they used on the atolls. This defense was well suited for these atolls which were often protected by offshore obstacles and reefs since the atolls were relatively narrow and a defense in depth was not practical. However, this defensive tactic was not well suited for the defense of Saipan.

On Saipan the terrain favored a defense along the beaches followed by a defense in depth, yet the Japanese defensive plan called for destroying the enemy on the beaches and that any foothold would be met be a fierce counterattack. The original Japanese plan, given time, would have allowed the Japanese to focus the defenses on likely landing sites with well fortified positions and overlapping fields of fire. Further inland, a secondary defensive belt would have been constructed. Dummy positions would have been created on both the first and second defensive belts in areas where the Japanese were not able to fully man an effective defense. These dummy positions would have hopefully deceived the Americans into believing that an area was heavily defended and force them to instead attack the true Japanese defenses. Much of this defensive posture and 'hold the beach' doctrine was also probably due to the aggressiveness of the Japanese leaders and the fact that the men on Saipan had so little time to prepare a defense in depth may have driven Obata to order the defense to initially focus on the beaches instead.

H. Smith's plan for the invasion of Saipan was for two divisions to land abreast of each other on a small frontage of only two miles. This landing would be made on the west side of the island near the town of Chalan Kanoa. The plan was to have the two marine divisions conduct an extremely fast, almost blitzkrieg style of invasion that would carry the initial wave of tanks and tractors more than a mile inland.

H. Smith summary of the enemy situation that was prepared on 13 June stated that the Japanese only had at the most 17,600 troops on the island, of which only 11,000 were combat troops. Earlier in May, the estimate was of only 9,000 troops on the island. The enemy situation report also stated that the beaches in vicinity of Chanan Kanoa were well defended by trenches, pillboxes, machineguns, and tank traps. This area would be defended primarily by infantry units while the rest of the island would be defended by non-infantry forces. Intelligence reports also led to the belief that the Japanese might have had some tanks on the island. The overall assessment was that Japan would strongly defend the beaches and conduct a mobile defense inland.

On 11 June, Task Force 58 launched 225 planes against the Southern Marianas and destroyed between 150 to 215 Japanese planes. The objective of this mission was to destroy both Japanese aircraft and air facilities. Over the next three days, the navy flew scheduled strikes against Saipan with the further goal of destroying coastal defensive sites and burning the cane fields south of Mutcho Point in order to facilitate the amphibious landing. During these three days another 50 planes were destroyed and 68 damaged.

Although the strikes did quite well in destroying the Japanese aircraft, the amount of damage done to the airfields and gun positions was limited. The airfields could be quickly repaired since they were mainly earthen in nature and only a direct hit would damage the gun emplacements. Due to the actions of the air strikes from 11-15 June, the Japanese aircraft create more than a slight nuisance against the landing force during the entire Marianas Campaign.

On 11 June, after the first day' of air strikes was over, Saito did not believe that the invasion of Saipan had technically began. It is important to note that at this time, Obata was not present on Saipan and was instead in the Palau Islands. Perhaps if Obata had been present, the indications that the invasion had started would have been recognized by the Japanese. In fact, at 1600, Saito, who was worried about the lack of a road between Marpi Point and the Aslito airfield ordered that a road be constructed between the two points. If Saito had properly assessed the buildup of submarine activity in the preceding months and the devastating air attack, he might not have had his engineers engaged in building a road when they could have been working on defensive positions instead.

On 13 June, seven fast battleships and eleven destroyers began the initial naval bombardment at 1040. This bombardment, which lasted until 1725, focused heavily on the defenses inland of the landing beaches and on Garapan and Chalan Kanoa. These two towns were essentially destroyed during the bombardment, but the overall effect of the naval fire on the troops and the defensive positions was minimal. The ships had to fire from at least 10,000 yards off the Saipan coast since they were unsure of the presence of naval mines nearer the island. Due to this fact, the ships were only able to target large buildings since this was all that could accurately be observed. However, during the bombardment, minesweepers swept the area west of Saipan as close as 2 miles from shore and found no mines. During the night the naval bombardment continued, but on a lower scale.

On the 14^th, seven large battleships, eleven cruisers, twenty-six destroyers and several other ships recommenced the bombardment. The efforts of the minesweepers the previous day allowed the ships to maneuver closer to the island. This reduced range allowed the naval gunfire from the ships to be much more accurate. However, even after the end of the day's bombing, many of the Japanese beach-line defenses were still capable of being defended. Also on the 14^th, three naval underwater demolition teams (16 officers and 80 men each) approached Saipan during the day while the naval bombardment was occurring. The purpose of these teams was to scout for any underwater obstacles, destroy them, and identify any obstacles on the beaches themselves. After their return to the ships they reported that there were no obstacles either in the water or along the beaches. Of curious note is that these men had to have seen the bamboo stakes in the water and on the beaches, yet they may not have realized their purpose since they did not include them in their report or remove the ones in the water. Although these men were able to identify that the beaches had no obstacles, their presence was noted by the Japanese who believed they now knew where the invasion would occur. Shiato predicted that the invasion would occur either that night or early the next morning.

On the night of 14-15 June the intensity of the fire died down and the transports, carrying the 2^nd and 4^th Marine Divisions, approached Saipan from the west. At 0530, the naval bombardment began again in earnest. At 0545, H-hour was announced to be at 0830 as scheduled. Around 0700 thirty-four Landing Ship Tanks (LST) with the assault battalion moved to the debarkation line (4,250 yards from Saipan). As they approached the debarkation line their doors opened and hundreds of amphibious tanks and tractors entered the water. Behind these LSTs were twelve additional LSTs loaded with light artillery. Behind them were the Landing Craft Mechanized (LCM) that would take the tanks and heavy artillery to Saipan as soon as the beach was secure. Behind these were the larger troop transports with the reserve forces and miscellaneous supplies and equipment.

At 0700, carrier planes comprising fifty-one scout bombers and fifty-four torpedo bombers attacked the beaches. Their goal was to demoralize the Japanese defenders more than to destroy any particular site. At 0730 the naval gunfire, which had stopped at 0700 to allow the planes to attack, recommenced.

At approximately 0800, the twenty-four assault Landing Craft Infantry (LCI) headed toward Saipan. The H-hour had been postponed to 0840 by this time due to problems with the launching of the amphibious vehicles. Around 0805, the amphibious tanks and tractors began their movement toward the beaches. Seventy-two planes attacked the beaches as the first waves of the amphibious landing force was approximately 800 yards from the beach and then these aircraft shifted their attack inland as the tanks and tractors were within 100 yards of the beach.

The main attack of the Marine Divisions was centered near Chalan Kanoa, just as planned. The 2^nd Marine Division was to land at Red and Green Beaches north of the town while the 4^th marine Division would land on Blue (opposite the town) and Yellow Beaches. As with most amphibious operations, not everything went as planned. The tractors moved faster than the tanks and in several cases blocked the ability of tank to fire. 2^nd Marine Division's landings in the south were made slightly to the north of their planned objectives, this caused a gap to occur between the flanks of the two divisions. Although the original plan had allowed for a small gap between the two divisions, the northward landing of the 2^nd Battatlion, 8^th Marines more than doubled the size of this gap. By 0907, the first wave had reached the beach with only minimal losses and 8,000 marines were ashore.

Besides the large gap between the two divisions, another problem that occurred during the landing was in the use of the amphibious tanks and tractors. In the 2^nd Marine Division's area, the tanks were to move ahead of the tractors and advance inland about 1,500 yards and then set up defensive positions and lay down defensive fire while the initial wave of tractors moved up to this defensive line and the troops off loaded. The second - fourth waves were to unload their troops on the beach. In the 4^th Marine Division area, the tanks were to lead the first two waves of tractors all the way to the objective, about a mile inland on some high ground. These tanks would then support the troops as they moved inland. The follow-on would be unloaded at the beaches.

In general, although most of the tanks and tractors made it to the beaches unharmed, the combination of their thin armor and slow movement made them easy targets for the Japanese artillery once ashore. The amphibious vehicles were under-powered and were easily stopped by obstacles (loose sand, trenches, holes, and trees) that normal tanks would not have had a problem with. This significantly slowed the movement of the amphibious vehicles. The lack of suitable paths inland from the beaches also inhibited the inward movement of the marines. By nightfall, despite the various delays, both divisions were fully ashore and had established a defensive belt over 1,000 yards deep and over 10,000 yards long. Seven battalions of artillery had also landed and so had two heavy tank battalions. Division command posts were also established ashore. One of the benefits of using the troop carrying amphibious tractors was that it allowed the men to be carried ashore in armored vehicles, rather than having to wade ashore as at Tarawa.

The Japanese had killed or wounded many Americans during the invasion, but the exact numbers for D-Day are unknown. The Marines had landed against the strength of the Japanese defensive area and at a time when four battalions of men who had not had time to move to their assigned positions elsewhere on the islands were located in vicinity of the beaches! The landing area was well registered for artillery and the Japanese had sixteen 105-mm, thirty 75-mm, and eight 150-mm guns on the high ground overlooking the beaches and were extremely accurate due to the pre-registration of the guns and the use of the bamboo sticks to help in adjusting fire. Yet, the Japanese artillery could have been more effective if they would have practiced concentrating their fire and not simply firing each weapon individually wherever the commander of the gun wanted to fire. On the first day, the Japanese relied almost solely on artillery, heavy weapons, and a few tanks to defeat the marines on the beaches. The infantryman rarely saw battle on D-Day.

To H. Smith's G-3, the most critical phase of the Battle for Saipan was the fight on the beaches. To succeed the marines had to establish a beachhead into which sufficient troops, heavy equipment, and supplies could be brought ashore. On the first day, the marines gained control of the beaches, but they were not secure since artillery and heavy weapons were still able to attack men and equipment on the beach. It would take six days before the beachhead was actually secure. One of the major problems was the gap between the 2^nd and 4^th Marine Divisions at Afetua Point and on the outward flanks of each division. This gap, which should have been closed the first day, took three days to close due to it being larger that originally planned thereby allowing the Japanese to defend this area in greater strength than expected.

By the night of the 15^th, the Japanese knew that they had to drive the Marines back to the sea. Yet, Saito believed that the landings might be a feint and only ordered minor counterattacks against the marines. He wanted to save his major forces in case the Americans did launch an invasion near Magicienne Bay. At 2000, a large force of Japanese infantry, supported by tanks, attacked the left flank of the 6^th Marines of the 2^nd Marine Division. Fortunately for the marines, naval gunfire firing illumination rounds were able to light up the sky enough to allow the defending marines to see the outlines of the Japanese soldiers as they attacked. The marine's machineguns and heavy rifle fire, along with the assistance of a battalion of 75-mm howitzers, were able to stop the Japanese counterattack. At 0300, another attack was launched against the same area, but it also failed. Before daylight, tanks and infantry again attacked the defending marines. By this time, a few of the medium tanks were ashore and able to help the marines stop the Japanese third counterattack against the 2^nd Marine Division.

The attack on Saipan, originally designed to overwhelm the Japanese with naval gunfire and rapid landings, failed on the first day. On this one day, the Marines failed to advance inland to their initial objective and were generally only 2/3 of the way to their objectives. An estimated 2,000 men were either killed or wounded and over 25% of the tractors and tanks were damaged or destroyed.

H. Smith, knew that a naval battle between the Japanese Mobile Fleet and the American 5^th Fleet was most likely going to occur in the near future. Realizing this, he was determined to get as many supplies and men ashore as possible before the protective battleships, cruisers, and destroyers departed with the carriers to met the Japanese fleet. On the evening of the 16^th, the 27^th Infantry Division landed on Saipan. Their mission was to capture Aslito airfield and to cut off the Japanese in the southeast corner of the island. Meanwhile, the 2^nd and 4^th marine Divisions would continue their attack inland. By the fourth day the Japanese had given up on trying to defend the beaches and had moved inland to set up defenses in the hilly and mountainous terrain.

In the meantime, after the landing of the 27^th Infantry Division, the majority of the 5^th Fleet departed the Saipan area as H. Smith had figured they would. On 19 June to 21 June the 5^th Fleet met the Japanese Mobile Fleet and defeated the Japanese fleet in the Battle of the Philippine Sea. Because of this naval battle, the Japanese on Saipan could expect to receive no further assistance. They were cut off from Japan and would have to fight out the battle for Saipan on their own. From this point onwards, it was believed by both sides that the American forces would defeat the Japanese on Saipan, the only question was how long would it take and how many men would die.

By 18 June, the 27^th Infantry Division had captured Aslito airfield. On 20 June, the command of the invasion force passed from Turner to H. Smith. From the 15^th to the 22^nd, the Japanese aggressively fought the American attacks as the marines attempted to push across the island and cut it in half. Casualties on both sides were extremely high and men were being slowly worn down and becoming combat ineffective.

Understandably, H. Smith could not afford the luxury of allowing his men the time to rest and the battle raged on. One of the most critical battles was the capturing of Mount Tapotchau. H. Smith had initially ordered the two marine divisions to capture the mountain. However, by 21 June he realized that he needed more men in order to capture this vital landmass since the Japanese were strongly defending it. On 21 June, H. Smith ordered R. Smith, commander of the 27^th Infantry Division, to move his division and insert it between the two marine divisions in order to conduct a three division abreast attack on Mount Tapotchau. H. Smith ordered the 27^th Infantry Division to fight generally up the mountain itself while the 2^nd Marine Division continue to move northeast and the 4^th Marine Division attacked eastward on the Kagman Peninsula, a relatively flat area but with plenty of Japanese defenders.

After two days of fighting, the division attack against the main Japanese defensive belt had stalled. The 2^nd Marine Division was on the outskirts of Garapan and near the summit of Mount Tapotchau. The 27^th Infantry Division had made very little progress against the stiff Japanese defense amongst the rugged terrain. The 4^th Marine Division had overrun the majority of the Peninsula and was nearing the eastern side of the island. However, the main Japanese defense on Mount Tapotchau remained. The American forces were now bent into a U-shape, with the 27^th Infantry Division at the center of the U with the two marine divisions at each end. This bend was over 1,500 yards deep and exposed the flanks of the marine divisions to attacks by the Japanese. During these two days of fighting the 2^nd Marine Division lost 333 men, the 27^th Infantry Division lost 277 men, and the 4^th Marine Division lost 812 men. During this battle, the American artillery and tanks were generally useless in a jungle environment filled with broken terrain. The fighting was mainly man-to-man with mortars and machineguns providing the heavy firepower. Close air support was not overly present due to the Battle of the Philippine Sea and was of limited use against the Japanese infantry in any case. Only direct fire and small assaults could defeat the Japanese soldiers who were hiding in caves, ravines, and gullies.

On 25 June, H. Smith decided that the poor performance of the 27^th Infantry Division was due to its lack of command and he decided to ask that R. Smith be relived of his command. After he talked this over with Turner the two of them approached Spruance. H. Smith stated that R. Smith had issued orders to units not under his command and contravened H. Smith's orders. H. Smith also stated that the 27^th Infantry Division was late in conducting its attack on Mount Tapotchau and therefore it slowed the movement of its flanking marine divisions, causing them to suffer unnecessary losses.

The relief of R. Smith probably did not make any real difference in the aggressiveness of the 27^th Infantry Division. However, it did stir up a Marine Corps / Army controversy. On Saipan itself, marines began to look down on the 27^th Infantry Division soldiers and the army soldiers resented H. Smith for relieving their commander and the implications made on the fighting capability of the division. Off of the island the controversy grew much greater, with several Army generals going so far as to recommending to Lieutenant General Robert C. Richardson, commander of all Army forces in the Pacific, that H. Smith was extremely prejudiced against army forces and that no Army forces should ever be put under his command again!

Major General Sanderford Jarman, who was on Saipan to take charge of the garrison operation after the Japanese were defeated, assumed temporary command of the 27^th Infantry Division from 24 to 28 June. On 28 June, Major General George W. Griner, Jr. assumed command of the 27^th Infantry Division. However, when he assumed command of the division, he was surprised to find out that he only had control of four infantry battalions, the rest of the division was under Corps command. Griner was told by H. Smith that he would have to "earn" the rest of the division back. By 5 July, the 27^th Infantry Division and the 4^th Marine Division had captured Mount Tapotchau and had pushed northward up the narrowing island. Due to this narrowing of the front, the 2^nd Marine Division was pulled into reserve. By 6 July, Griner regained the control of all of the 27^th Infantry Division's units. On 7 July, three thousand Japanese soldiers conducted a bonzai charge against the 27^th Infantry Division. The Japanese soldiers were armed with only grenades and bayonets, yet they broke through the 27^th Infantry Division on the western flank near the coast. The Japanese soldiers destroyed two infantry battalions and were only stopped by marines of the 2^nd Marine Division after the Japanese had passed through the 27^th Infantry Division's sector. By this time, H. smith had had enough of the 27^th infantry Division and various reports state that he ordered the entire division withdrawn from Saipan. In reality, only the decimated battalions were withdrawn from Saipan by destroyers. However, H. Smith did order the 27^th Infantry Division into reserve and vowed that he would never use the division again.

By 9 July, the 4^th Marine Division was at the northern tip of Saipan and H. Smith had declared the island secure from any significant organized resistance. By this time, almost 24,000 Japanese troops were known to have been killed and 1,780 captured. The United States lost 3,426 men killed and 13,099 men wounded; a casualty rate of 25%.

Earlier, on 22 June, the governor of Saipan had received a message from the Imperial Palace informing him that any civilian that died fighting the Americans would be granted the same afterlife privileges of the soldiers who died for the Emperor. Saipan was the first island encountered by the Americans that had a large number of Japanese civilians on it. The Japanese Government used propaganda that often showed the Americans as monsters. The naval and air bombardment, followed by three weeks of tough fighting did not dispel the fears of the Japanese civilians. Of the twenty-two thousand civilians on Saipan, thousands these civilians fought against the Americans during the battle for the island. As the Americans pushed northward, the civilians fled before them. By the time the Americans reached the northern end of Saipan on 9 July, thousands of Japanese men, women, and children were at the top of the cliffs overlooking the shark-infested waters. Once there, many of these civilians realized that they were cornered, and rather than surrender to the Americans, they dove off the cliffs into sure death in the water below. Out of the twenty-two thousand civilians, approximately eight thousand died in this lemming-like act. However, marine interpreters with loudspeakers did convince many of the Japanese civilians to surrender.

On 20 July, after engineers had made extensive repairs to and lengthened the runway of Asltio airfield, now renamed Isley Field, it received its first American plane. By early September B-24s were conducting missions against the Bonin Islands from Saipan. A second airfield was constructed to handle the larger B-29s. In October, the first B-29 raid from Saipan was flown against Truk. Saipan not only served as an airbase for attacks against other Japanese islands, but it also became an important naval base, particularly for submarines that would ultimately operate in the Japanese home waters.

As a note, although I am an Active Duty U.S. Army Warrant Officer, none of the opinions / views expressed in this article reflect those of the US Army or the Government of the United States of America.  I wrote this article while working on my Master of Arts in Military Science from American Military University, where I am now an adjunct professor of U.S. and Military History.  While I wrote this article for a class, I placed it on the internet simply to help inform people about the Battle for Saipan.                             Brian D. Blodgett

Mr. Blodgett has asked me to pass along his website and welcome everyone to visit https://sites.google.com/site/blodgetthistoricalconsulting/the-invasion-of-saipan