ICYMI: Battle of Saipan and the IJA 43rd Division on WW2TV!
- Tony Boccia
- Jun 14
- 11 min read
Greetings all, I recently appeared on WW2TV with Paul Woodadge to discuss the invasion and battle of Saipan from the perspective of the Imperial Japanese Army garrison defending the island. We had a really good chat and in case you missed it, here's a link to the video below. I've also included the show notes, in the event this is something you are interested in and would like to know more. You can learn about Saipan, and the Northern Marianas Islands in general, right here at the Pacific History Guide. Happy reading, I hope you enjoy!
Show Notes
Introduction
Hello WW2TV fans, it’s great to be back here with you. Thanks Woody, for the invitation and warm welcome. If we’re meeting for the first time, I’m Tony Boccia, an active-duty U.S. Naval Officer with a specialty in aviation maintenance. I’m currently stationed in San Diego, California. I’m a historian, primarily focused on Imperial Japan, the expansion of that empire into the Southern Seas, and the rise and fall of the Imperial Japanese Navy. I was stationed in Japan for fifteen years and Guam for three, prior to San Diego.
I’m also the creator of Pacific History Guide, a website designed with military servicemembers and their family members in mind; the goal is to help connect people with history, where they are. Please check it out and give us a like on social media.
This is my second time on WW2TV and I’m so pleased to be back. Today I’ll be discussing the state of Japanese forces in and around Saipan in the summer of 1944 and the point of view of Lt. Gen. Saito Yoshitsugu, who as commander of the 43rd Division was charged with the island’s defense.
In this talk, we’re going to brush past the battle of the Philippine Sea; in this battle the Imperial Japanese Navy lost some 600 aircraft and three carriers. The Japanese plan to defend the Central Pacific was to lure the Americans into a battle in which they’d be forced to confront land-based aircraft, the Combined Fleet, and the garrison ashore, and be destroyed.
The loss of Saipan pierced Japan’s ultimate defense zone. From November 1944, B-29’s were a frequent site over the home islands, launched from airfields on Saipan and nearby Tinian
Background
Some quick background: Saipan in 1944 had been under the charge of Imperial Japan for nearly 30 years. From the Japanese near-bloodless conquest of German-held Micronesia in 1914, and the grant of a mandate in Paris in 1919, Japan remade Saipan in her image as a propsperous, organized part of the empire. Saipan was one of the major hubs for the inter-island and intra-Pacific trade throughout the Japanese colonial period, alongside some other now-famous islands; among them Kwajalein Attoll, Palau, Truk, Kosrae, and Majuro.
There were roughly 30,000 Japanese living on Saipan when the Americans showed up in June 1944, and most of them were working in the sugar industry; these plantations were mostly situated in the south and west. A small railway, constructed to support the sugar crop, ran throughout the island.
There is a mountain ridge running from the center of the island to its northern tip. The at the southern end of the ridge is Mt. Tapochau, the highest point on Saipan at 474 meters or 1,550 feet. Garapan, the capital, about midway up the west coast. The main sugar refinery at Chalan Kanoa is south of Garapan.
Status of Forces
Beginning in March 1944, Saipan was home to the Central Pacific Area Fleet (or Chūbu Taiheiyō hōmen kantai 中部太平洋方面艦隊). Falling back from the American invasion of the Caroline, Vice-Admiral Nagumo Chuichi was tasked with the defense of the Marianas and Palau.
The best days of Nagumo were far behind him. Chosen to lead the IJN’s air arm in April 1941, Nagumo was in command at the Pearl Harbor raid and Midway; his actions there (not destroying the shipyard at Pearl Harbor, misusing his carriers at Midway) led to a degradation of his career that matched the decline of the Imperial Japanese Navy and its Air Service.
Nagumo’s Imperial Japanese Army counterpart was Lt. Gen. Obata Hideyoshi, commanding the 31st Army. This had been established in February 1944 and sent it to Truk (now Chuuk) in the Carolines. The army’s codename 備 ‘Preparation’ was indicative of its purpose: to keep the Americans from continuing their push across the Central Pacific. At the time of the American landings on Saipan, Obata was elsewhere in the Japanese island territories, inspecting defenses on Palau. He was ordered by HQ to return to Saipan; finding that impossible he made his new HQ on Guam.
The poor relationship between the Imperial Japanese Navy and Army is well documented; Obata refused to place his army under Nagumo’s command, delegating operational command of the 31st Army to his Chief of Staff Major General Igeta Keiji. The 31st Army was comprised of the 43rd Division and the 47th Independent Mixed Brigade. The latter was comprised of small regiments, survivors of previously destroyed units, and stragglers. The special naval landing forces (SNLF) in and around Garapan had roughly 6,000 troops, under Nagumo’s direct control.
Igeta had a poor relationship with the commander of the 43rd Division, Lt. Gen. Saito Yoshitsugu. Poor command structure in the IJA exacerbated this; the two maintained separate HQ’s and did not speak to each other throughout the battle. Nagumo, irritated that Obata did not give him overall command of the 31st Army, refused to allow Igeta the use of his SNLF troops, but offered them to Saito, with whom he had a better relationship. Ultimately, the defense of Saipan fell to Saito, who took direct control of both the 43rd, 47th, and SNLF troops of the 5th regiment. Saito and Nagumo spent the entire battle together.
Saipan’s Defenses
Saito’s great task was to prepare for an enemy amphibious landing, which meant a great deal of manpower was required to dig out trenches, establish communication lines, and build bunkers. There were three great shortfalls staring him in the face. One, he lacked mechanized equipment to dig trenches, fortify caves, and move tanks and artillery. Second, much of the construction equipment needed was being sent to the bottom by American submarines; the 118th infantry regiment along with several transports of food, equipment, and supplies was torpedoed in early June. Finally, the Japanese high command was convinced that the next target of the Allies was Palau and the Western Carolines; they had anticipated the landings in November; five months later.
All told, Saito commanded approximately 25,500 army and 6,200 naval personnel across Saipan. While this sounds like a lot of people (especially considering with the civilian population the island had about 55,000), with the shortfalls previously discussed, he was not ready when the Americans showed up. In Garapan and Chalan Konoa there were crates of machine guns, shipping containers with small and medium-sized tanks, and a smattering of construction supplies, all unused on the morning of June 15th.
Saito had divided the island into four sectors, with the following layout:
Northern: Tanapang to Marpi point, 135th Regiment
Navy: 5th SNLF regiment and a battalion from the 136 Regiment
Central: Outskirts of Garapan (The capital) to Afetna point, interior to the central mountain ridge, 136th Regiment
Southern: 47th Independent Mixed Brigade
A captured IJA intelligence Officer later told the Americans that until D-Day, Saito was convinced that the landing beaches would be Magicienne Bay. As it turns out, the Americans feinted at Tanapang Harbor, then came ashore at Afetna point, south of Garapan and North of Agingan Point. (In the video I incorrectly said Afetna Point, please excuse this mistake)
The Central and Southern sectors of the IJA would feel the most immediate brunt of the American forces. Saito had only 29 large-caliber weapons, with a mix of 75 mm and smaller guns and howitzers. These were largely hidden inside caves and under cover on ridges so that they’d be invisible to American spotter planes. An example of the weapons used would be the Arisaka type 38 and type 99; type 38 machine gun, and type 11 70mm mortar.
D-Day 15 June
136th Regiment of the 43rd Division under Colonel Ogawa Yukimatsu opposed the 2nd Marine Division, which is pushing in and up toward Garapan and Mt. Tapochau. These troops had a mixture of rifles and mortars, they prevented the Americans from gaining a beachhead for about two hours; in time they were pushed back toward Garapan.
The 316th Batallion of the 47th Independent Mixed Brigade under Capt. Eto Susumu opposed 4th Division and 27th Infantry Division, pushing inland to Aslito Field. This unit fought hard, employing mortars and artillery pieces, along with expertly devised communication and transport trenches to use the rugged landscape to conceal their locations.
Between Chalan Kanoa and Olea was the ‘sugar dock’ on the coast near Lake Susupe; Japanese artillery units used this position to disrupt the landings; combined with the action of their counterparts further back in the jungle, approximately 164 amphibious tanks and other vehicles were destroyed the first day. The troops at the sugar dock held out until the afternoon of the 16th, when they engaged in hand-to-hand combat with the U.S. Marines and were destroyed.
(Note: in the video I incorrectly identified the location of the Sugar Dock as between landing beaches Red 3 and Green 1, it is actually between Green 2 and Green 3. You can see a rail track on the map that terminates at the coast there)
Japanese Counterattack
Night of 15-16 June, Col. Goto of 136th Regiment counterattacks the American beachhead with the goal of driving them into the sea. Goto’s unit of mixed armor and infantry was plagued by poor intelligence and a lack of communication and he did not have a solid understanding of where the American lines were or what troops were present. It was repelled with a loss of 700-900 soldiers.
On 17 June 1944 at 2:30 AM, a large counter-attack was performed by the 43rd division together with the 9th armored regiment of the 1st tank division. This time, the Japanese had between thirty and forty tanks. Most were medium Type 97 Kai Shinhoto Chi-Ha vehicles armed with a 47mm main gun and a couple of machine guns. A few were the smaller Type 95 Ha-Go armored vehicles with a 37mm main gun and two machine guns.
The tanks gave away their presence moving into their attack positions. The Marines heard the sounds of their engines, as well as the chanting and shouting of Japanese infantry, Although the Japanese were able to re-capture the local high ground, their gains were dramatically reversed in the morning of 18 June 1944, when the US forces captured Aslito airfield in the south of the island largely intact. The airfield was the primary objective of the invasion force; within days it was hosting USAAF and USN aircraft.
On the 18th, General Igeta, nominally in charge of IJA troops on the island, ordered a ring established around Mt. Tapochau; the 135th Infantry Regiment was deployed to the west and south of the mountain, and the survivors of the 118th Infantry Regiment and the 1st Battalion of the 18th Infantry Regiment were deployed to the east of it along the shores of Laulau Bay. This order, however, was not conveyed to General Saito, and as a result the troops required to build this defensive line were unorganized. It was largely ineffective.
By 24 June 1944, the 43rd division was reduced to four battalions of infantry and a half-battalion of artillery; 9,000 men in the 43rd division, 6,000 in brigades and other units. They had lost Garapan, Hill 192, and Hill 286 to the Americans. Although the IJA had been successful in slowing the American advance south and east of Mt. Tapochao, the ever-shrinking pockets of Japanese resistance were clearly not going to break out into any large force. The noose had been tightened around Mt. Tapochau to the extent that the only organized resistance was at the platoon and company level.
Status of Forces by 27th June
June 25th: A meeting of marshals had been convened in Tokyo on the 24th and the next day, the decision to abandon Saipan was made. The lack of support from the Combined Fleet made the decision for them; there was no way to reinforce or resupply the island. In the meantime, everyone in the Saipan garrison believed that the combined fleet would come to their aid.
June 27th: With Mount Tapochao occupied, the Saipan garrison forces held a joint command meeting to consider their future course of action. The conclusion was that the residents would be evacuated to the northern areas, and the military would set up resistance lines at Tanapag, Hill 221, and Talohoho, and fight to the end.
The 136th Infantry Regiment lost most of its troops in the previous days; it was unknown how many still survived or how to contact them. The remnants of the 118th Infantry Regiment and Kawamura Battalion, which had been strongly defending Death Valley, made it to the new defensive line, but were no longer able to fight. The survivors of the 135th Infantry Regiment also retreated, but the division staff had dug octopus traps and they set up camp there. The 135th Regiment had been using this area as a defensive position after landing on Saipan, so they were familiar with the terrain and were able to retreat smoothly. The 18th Navy Infantry Regiment, Ushiyama Unit, continued to put up a desperate resistance near Tanapag.
Meanwhile, the 317th Battalion, 47th Independent Mixed Brigade, isolated at Naftan Point, had been engaged in fierce fighting every day since the attack on Aslito Airfield on the 18th. Finally engaged by the U.S. Army which began firing directly into the caves, Capt. Sasaki on the 27th ordered a charge toward the airfield, directing his starving and dispirited troops to destroy the American aircraft and take control of the HQ there. All were eventually killed or committed suicide in the rout, which yielded no other results.
General Saito’s HQ
The 43rd Division headquarters had been located at Nanko Shrine since the 13th, but on the 18th, Division Commander Saito was ordered to take combat command of the entire island, and on the 19th he moved his headquarters to the north side of Mount Tapochao. On the 27th he radioed Tokyo asking for either reinforcements or evacuation by air. At that point, he estimated resistance could continue until 10 July 1944.
The End
July 2nd: At the final line of resistance, the headquarters ’defending forces are united and preparing for the final battle at the new defense’ he reported.
By 5 July 1944 the position of the 43rd division was hopeless, so Saito ordered to prepare for a suicide charge, starting at the dawn of 7 July 1944 with a force of 4,000 men, most of them already wounded. The 43rd division was annihilated in this ‘banzai’ charge, killing 658 US servicemen in its final day. The Americans call it a banzai charge because that’s what the Japanese were screaming, but actually the term is 玉砕 or gyokusai, which means ‘smashed jewel’, the word evokes an image of destroying something beautiful so that it won’t be taken or corrupted by anybody else.
Saito, Nagumo, and their chiefs of staff killed themselves when it became clear that the island was lost. Saito was given a funeral with military honors by his American counterpart Holland Smith. Nagumo’s body was never found. Some 22,000 civilians, conscripts, were killed on Saipan during the fighting; most were caught in the crossfire; others were murdered by the Japanese. More than 1,000 men, women and children committed suicide on Saipan as the Japanese lines shrunk back toward Marpi Point. The last Japanese resistance on Saipan ended on the 1st December 1945, several months after the end of the war, when Capt. Oba Sakae finally surrendered to American forces.
Although the Americans had made an effort to communicate that every captive would be cared for, the Japanese officials in and outside of the armed forces worked hard to convince them that the ‘ugly enemy’ would rape, murder, and even eat them and their children if taken alive. The suicide cliffs at Marpi Point bear more than a dozen memorials, some small, some large, to these innocent lives lost in the madness of war. I won’t include photos here; these things are best left to you to discover on your own.
I encourage all of you to visit Saipan if you’re ever in the Marianas. This is a place that is worth your time and effort to see for yourself. Thank you and I’ll take questions now!
If you made it this far, congratulations! I thank you for your kind support. Please look out for more talks on WW2TV, as we continue to study and teach the history of the Second World War.
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