- 72 - Pacific War - Operation I-GO, April 4-11, 1943

Last time we spoke about the disastrous first Arakan campaign and the Pacific Military conference of 1943. Yes Mr. Irwin had royally messed up the Arakan offensive, so much so it was gradually bringing his bitter rival General Slim into the mix. While Irwin failed, Slim gradually was placed in operation control and would soon unleash a box strategy against General Koga’s forces in Burma. On the planning front, the war between MacArthur and King raged on, but compromises were finally hashed out. The July 2 directive, became the Elkton plan which in turn would evolve into Operation Cartwheel. The allies were learning how to play nice together in the Pacific at last. MacArthur was gradually shifting the war towards his own personal goals. However while all of this was going on, the Japanese were also forming their own plans, which would soon be unleashed.

This episode is the Operation I-GO

Welcome to the Pacific War Podcast Week by Week, I am your dutiful host Craig Watson. But, before we start I want to also remind you this podcast is only made possible through the efforts of Kings and Generals over at Youtube. Perhaps you want to learn more about world war two? Kings and Generals have an assortment of episodes on world war two and much more  so go give them a look over on Youtube. So please subscribe to Kings and Generals over at Youtube and to continue helping us produce this content please check out www.patreon.com/kingsandgenerals. If you are still hungry for some more history related content, over on my channel, the Pacific War Channel you can find a few videos all the way from the Opium Wars of the 1800’s until the end of the Pacific War in 1945. 

It is April of 1943, a year ago, the Empire of the Rising sun stood proud and victorious over the Pacific. The Japanese had taken Malaya, the Philippines, the Dutch East Indies, Burma and pretty much anywhere they went, victory was at hand. Yet as Admiral Yamamoto moved his flag from super battleship Yamato to the Musashi, he looked quite withered down. The past 14 months since the great raid on Pearl Harbor had aged him considerably. His close-cropped hair had turned almost entirely gray and his eyes looked discolored. It was rare to see him leave his quarters and whenever he did it was quite briefly, usually him waving his hat in the air as a departing sign to a squadron of aircraft. Rarely did he join his fellow staff officers for a game of ring-toss on deck. In a letter he wrote at the end of January of 1943 he asserted he only set foot ashore 4 times since the previous august, only to check in on the sick or wounded men at the hospitals or to attend funerals. Critics of Yamamoto would claim he actually made considerable amounts of visits to the “naval restaurant” on an island in the lagoon. This “naval restaurant” was actually a well-known brothel near Yokosuka Naval base in Tokyo Bay.

The commander in chief seemed resigned to his fate. When he was asked in October of 1942 what he would do after Japan won the war he replied “I imagine I’ll be packed off either to the guillotine or to set Helena”. On most occasions he would openly declare he did not believe he would live through the war. Yamamoto mourned the loss of so many IJN officers and sailors and was especially saddened by the loss of the commanders who refused to leave their doomed ships. Yamamoto had actually campaigned to reform the principle that a captain could and should honorably survive the destruction of his ship, but it was to little avail. The belief was so hard-wired into the Japanese naval officer corps. 

Yamamoto knew Japan was staggering towards a catastrophic defeat, but he could not openly say it to those around him. He had tossed everything he could to thwart the war in the first place, warning everyone of the great industrial power of America that would gradually overwhelm Japan. His operation against Midway in june of 1942 was a major gambit aimed at forcing a decisive victory to bring the Americans closer to the negotiating table. The utter failure at Midway had ensured the war would be prolonged, it would become a war of attrition and one that Japan could not hope to win.

On the morning of April 3rd, 1943 Admirals Yamamoto and Ugaki accompanied by more than a dozen officers of the combined fleet staff boarded two Kawanishi flying boats enroute for Rabaul. The battles of Guadalcanal and Buna-Gona-Sanananda were extremely heavy setbacks to Yamamoto’s plans of extending the defensive perimeter towards the east of Australia so it could be strangled of supplies. The disaster that occurred at the battle of the Bismarck Sea showcased how vulnerable their shipping lanes were. The state of their land-based aviation was abysmal, it failed to protect the convey sent to Lae resulting in the terrible loss. As Commander Toshikazu Ohmae stated “The land-based air groups at Rabaul were not effective, largely because there were only a few experienced pilots in them.  Vice-Admiral Ugaki was even harsher, adding “We cannot expect much of the land-based air force partly because of a passive atmosphere among them.” 

Admiral Kusaka’s 11th air fleet had suffered tremendous losses from a series of serious ongoing issues, but two were of vital importance; 1) the poor health and low morale of those at Rabaul. Men were succumbed to widespread diseases, such as malaria and chronic diarrhea. And 2) the terrible situation when it came to replacing men such as their valuable veterans. As Yamamoto put it “They used to say that one ‘Zero’ fighter could take on five to ten American aircraft, but that was at the beginning of the war. Since losing so many good pilots at Midway we’ve had difficulty in replacing them. Even now, they still say that one ‘Zero’ can take on two enemy planes, but the enemy’s replacement rate is three times ours; the gap between our strengths is increasing every day, and to be honest things are looking black for us now.” The new recruits were unfamiliar with the aircraft employed by Kusaka’s command, requiring to be re-trained upon their arrival to Rabaul. Without their veteran pilots to train these men the task took longer and resulted in less capable pilots and crews.

The replacement issue for aircrews was a fleet-wide issue forcing the IJN to shorten their training syllabus for commissioned and enlisted pilots by 2 months. To achieve this reduction, the amount of instructional time devoted to skill areas like tactics, gunnery and formation flying were reduced or in some cases even eliminated. The veterans who began the war in a third position of a 3-plane sector and were still alive now took upon the role of shotai or chutai leadership. Shotai leaders were responsible for flights of 3 aircraft and Chutai leaders were responsible for 9 aircraft or better said 3 shotai. However many of these men did not really have the necessary experience to assume such responsibilities.

On March 25th a directive was established to quote “create a superior and impregnable strategic position”. In other words, Tokyo was demanding the Army and Navy come up with a plan to stop the allies southern offensive. Tokyo wanted the two services to actually work together so they could defend the precious gains they had made in the early part of the war, like their holdings in New Guinea which were currently being hammered upon by MacArthur's forces. To implement the new directive, General Imamura summoned a conference on Rabaul for April 12th. Commanders of the 17th and 19th armies, the 6th air division would be in attendance. During the conference it was decided General Hyakutakes 17th Army would take on the responsibility for defending the northern solomons in coordination with the Navy. They would also have to help assist the navy who was expecting allies attacks directed at the central solomons. General Adachi’s 18th army was given responsibility to defend Lai-Salamaua, but because of the shipping lane crisis this would have to be done mostly via land routes. They were going to establish a major overland and coastal supply route linking Madang and Western New Britain to the Lae area to aid this. Furthermore naval and air bases would be built up in eastern New Guinea to aid Lt General Itahana Giichi’s 6th air division to operation in the region. Despite all these grand plans, American air power was already making Tokyo express runs to places like Finschhafen impossible. The Japanese war effort in New Guinea was gradually being torn apart by constant air raids. Therefore, the only way to get men and supplies to places like Lae would be using the ever glamorous submarine or barge methodology. Now that is all for the Imperial Japanese army boys planning session, but what about Yamamoto and the Naval gang.

By the time of the conference, MacArthur’s efforts in New Guinea had basically ruined Yamamoto’s expansionist strategies. A complete strategic rethink was now necessary. Yamamoto was quartered in a cottage high on a hill behind the town of Rabaul. He spent the following week inspecting airfields and other military installations, meeting with the local army and naval commanders all around New Britain. As was typical of him, he bid good luck to the departing air squadrons, with his usual wave of his hat. Yamamoto set to work creating a new offensive directive erected as part of the March 25th plan. The IJN planned for an air campaign against allied positions in New Guinea and the Solomons. The 11th air fleet, on its lonesome would not able to mount an effective strike, thus Yamamoto called upon the 3rd fleet to augment them.  Admiral Ozawa who led the 3rd fleet voiced opposition to this, not wanting his precious elite units to be squandered. But he eventually gave in and provided aircraft carriers and agreed to supervise plans for the new operation. At the same time it was decided that Yamamoto and Ozawa would shift their headquarters temporarily to Rabaul, this would prove to be a fateful mistake on his part. You see him doing so was announced using a radio message. His operations officer Commander Yasuji Watanabe would go on the record complaining that the information about Yamamoto’s visit to the Ballalae Airfield should had been done by courier and not by radio, but the communications officer replied “this code only went into effect on april 1st and cannot be broken”. It would be broken, but more about that later. Now the Zuikaku, Zuiho, Junyo and Hiyo would toss up 160 aircraft: 54 Vals, 45 Kates and 96 Zeros to augment the 155 aircraft of Admiral Kusaka pushing them to a strength of over 350 aircraft. The aircraft were dispersed to multiple airfields such as Buka and Kahili on Bougainville and Ballale in the Shortlands.

 

Now before Yamamoto and his team launched their new offensive, Admiral Kusaka decided to do a preliminary fighter sweep down the Slot on April 1st. He hoped to draw out large portions of the allied airpower on Guadalcanal to soften them up. Kusaka launched a first wave of 32 and second wave of 25 Zeros which intercepted 42 fighters of Admiral Mason’s ComAirSols command. The allied force consisted mostly of Wildcats, some P-38’s and a few new F4U Corsairs. They were intercepted over the Russell Islands causing a giant melee of dog flights lasting over 3 hours. The Americans had home field advantage over the Japanese, managing to shoot down 9 Zero’s at the cost of 5 Wildcats and a Corsair. It was not exactly a promising start for the Japanese. As usual both sides of the air battle submitted exaggerated reports. The Americans claimed to have taken down 18 Zeros and the Japanese claimed to have downed 47 American fighters. So yeah the Japanese claimed to have shot down more aircraft than they even encountered haha.

Now it was on April the 3rd when Yamamoto and his staff arrived in Rabaul and he personally took command of the upcoming operation alongside Admirals Ozawa and Kusaka. Now Yamamoto had accurately anticipated the allied advance into the solomons and New Guinea would focus on the subjugation of Rabaul. Within five days of the battle of Guadalcanal being officially declared on February 9th of 1942, Lt General Kenney had authorized a plan to take down Rabaul. This plan commence on the night of February 14th with a bombing raid consisting of 12 B-29’s from the 63rd bomb squadron. They targeted the fuel dumps and munitions. A second wave of 10 B-29’s from the 65th bomb squadron came in dropping incendiaries upon the town of Rabaul. The Japanese had managed no fighter interceptions. Yamamoto had further predicted the allies would launch a double-pronged advance through New Guinea and the northern Solomon islands. To meet this advance he had set up a ring of airfields around Rabaul. His visit to Ballalae airfield was part of developing the rings and it would be his death sentence in the end. The result of these plans led to a triangular combat zone with Port Moresby on its west point, Guadalcanal at its east and Rabaul as its northern apex. 

Yamamoto knew the US forces would advance under the cover of air superiority which in turn depending upon their ability to build forward airfields. In anticipation of his Yamamoto had as we mentioned gathered a massive build up of aircraft with the intent to hammer the allies ability to supply materials and build further airfields. The battle for Henderson field on Guadalcanal was the first of these contests and many would follow. Yamamoto hoped the shorter lines of supply from airfields closer to Rabaul would give them an advantage over the Americans, but despite all the claims of great air victories, Yamamoto’s personal tour was revealing the opposite. In fact, as Yamamoto used the post-guadalcanal lull in action to bolster his defenses for a anticipated battle ahead, Halsey had likewise prepared his forces for their advance into the central and northern solomons. 

Halsey would have a number of new toys to play with such as the Chance Vought F4U Corsair and Grumman F6F Hellcat. 4 new airbases were built upon Guadalcanal and during march of 1943 allied bombers made sporadic attacks on the Japanese airfields at Ballalae, Kahili, Shortland Island and Munda. On top of that large scale reconnaissance efforts were made to get a good picture of the Japanese build up of their airfields. When reconnaissance found out the Japanese were developing a seaplane off southern bougainville, the Japanese launched a dawn fighter attack on March 28th. Led by Captain Lanphier of the 70th squadron, 6 P-38’s destroyed 8 Japanese seaplanes. Now after a week of sporadic bombing raids from both sides, allies watchers on the New Guinea coast indicated a major offensive was afoot. 

Yamamoto’s grand air campaign was codenamed operation I-GO with attack day X set for april 5th. The first target was to be guadalcanal, but bad weather forced a postponement of 2 days. Japanese reconnaissance since March 25th had indicated the allies had roughly 300 aircraft on the island, alongside transports, cargo ships, warships and other goodies going between Lunga Point and Tulagi. In the early hours of April the 7th, Yamamoto unleashed a massive strike force consisting of over 224 planes, the largest striking force since the attack on Pearl Harbor. 67 Vals and 157 Zeros were enroute to smash Guadalcanal.

But the allies enjoyed great intelligence and received several warnings of the impending offensive. The coastwatchers were hard at work transmitting their sightings. Rear-Admiral Marc Mitscher , the new commander of AirSols scrambled 76 fighters consisting of Wildcats, Lightnings, Airacobras and Kittyhawks from Hendersonfield, Milne Bay and other outlying airfields. Despite the prior warnings, the allied scramble was rather disorderly and to make matters worse the Japanese cleverly split up their attack force into 4 groups to confuse the allied radar systems. 4 squadrons of Vals were preceded by 2 sweeps of Zeros which were intercepted by 3 squadrons of Wildcats. Marine 1st Lt James E Sweet of the VMF-221 was credited with shooting down7 Vals and possibly an 8th using his Wildcat. His aircraft was badly mauled during the combat forcing him to make a water landing outside Tulagi harbor. He would be awarded the Medal of Honor for this great feat. 

Despite valiant efforts made by the allies, the Vals laid havoc to the Tulagi anchorage. The destroyer USS Aaron Ward, New Zealander corvette Moa and US tanker Kanawha were sunk. THe crews over in Henderson field were fortunate as it was not hit too hard as the dog fights broke up the Japanese Vals and Zeros who were forced back towards Bougainville. For their efforts the Japanese lost 12 zerosand 12 vals. The Japanese pilots claimed to have downed 41 allies aircraft, which turned out to be 7 Wildcats and 12 major warships which were the 3 previously mentioned. With what seemed to be a large success for operation X, Yamamoto felt confident and decided to launch operation Y of I-GO.

While operation X of I-GO was directed at Guadalcanal, operation Y would hit New Guinea. On april 11, 27 Vals and 73 Zeros departed Rabaul to hit Oro Bay which was adjacent to the rapidly expanding airdrome complex at Dobodura. The allies scrambled 50 aircraft consisting of Lightning and Warhawks of the 7th, 8th and 9th squadrons. The vals managed to sink a US cargo ship, heavily damaging a transport and an Australian minesweeper. The next day Yamamoto traveled to Vanukanau airdrome to personally send off another strike and announced he would do a tour of the forward bases of Buin, Ballale and Shortland island. The signal was picked up by allied listening posts. Cryptanalysts at Station Hypo led by Joseph Rocherfort decrypted the message and pronounced it a jackpot. The message referred to Yamamoto was easily deduced, and the geographic designators for Rabaul, Ballale and Buin were easily extracted. Better than that the message contained the specific information that Yamamoto would be traveling on a medium bomber escorted by 6 fighters, and would arrive at RYZ at 8am. This would put Yamamoto’s aircraft over the southern end of Bougainville on the morning of the 18th, a location just within the fighter range of Henderson Field. I will not be speaking anymore of this as it will be discussed in depth in a future episode, just a tease I know.

At Vanukanau Yamamoto presented himself in his crisp white uniform, waving his hat to the crews of 43 Bettys followed up shortly by 65 Zeros. A second group of 66 Zeros assisted the raid to perform a sweep, leaving a combined total of 174 aircraft. They flew in two large formations with an initial course direction going towards Milne Bay. Allied radar picked them up prompting General Kenney to scramble every fighter had in the area. However the course the Japanese took was a feint and without warning they broke out going across the Owen Stanley range enroute for Port Moresby. 44 allied fighters were able to intercept them, but many of the bombers managed to get past them. The bombers hit the airstrips, damaged installations alongside 15 grounded aircraft. The Japanese would claim sinking a transport anchored in the harbor and the destruction of 28 enemy planes in the sky, though only two P-39’s were shot down at the cost of 2 Zeros and 7 Bettys. 

On april the 14th, Yamamoto again personally waved off another attack, this time targeting Milne Bay. 23 vals and 75 Zeros were launched from carriers Hiyo and Junyo joined by 54 fighters and 44 Bettys from the 11th air fleet for a total of 196 aircraft. Here the Japanese scored some luck, because as a result of the air raid against Port Moresby the allies had actually rerouting most of their shipping to Milne Bay. The allies scrambled 44 fighters, 36 Kittyhawks from Milne Bay and 8 lightnings from Dobodura to intercept them. Despite the efforts of the allied airmen, Japanese bombers broke through making their way to Milne Bay in several waves. The high level bombers dropped at least 100 bombs over the anchorage, while the dive bombers attacked the allied shipping. The Dutch troop transport Van Heemskerk was forced to beach itself after suffering several hits lighting her ablaze; the British cargo ship Gorgon was also hit many times and lit on fire; the Dutch transport Van Outhoorn and Australian minesweepers Wagga and Kapunda were damaged by near misses. In the battle in the sky one Kittyhawk was shot down, 4 p-40’s were severely damaged and 1 lightning was forced to make a crash landing.

The Japanese claimed to have sunk 3 large and 1 medium transport, heavily damaged 6 transports and shot down 44 aircraft. During the air battle one Lt Richard Bong was starting to make a name for himself having shot down a pair of Betty’s. He would earn a lot of attention from General Kenney who described him “as a little blonde-haired Norwegian boy. Best watch the boy Bong”.The Japanese claims was so incredible, upon hearing of it Emperor Hirohito sent a message stating “please convey my satisfaction to the commander in chief, combined fleet, and tell him to enlarge the war result more than ever”. To contrast this, General Kenney made some remarks about the intense air raids “the way yamamoto had failed to take advantage of his superiority in numbers and position since the first couple of month of the war was a disgrace to the airman’s profession”. The reason he had this scathing remark was because apart from the rare exception of mass attacks, the Japanese attacks were marked by their use of aircraft in Penny-packets. What Kenny did not know was how the IJN’s air forces were being hampered heavily by logistical issues. Their inability at this time was a result of lack of experienced aviation engineers, ground crews, adequate airfield facilities and airfield equipment. They simply were not the same aviation force that had hit Pearl Harbor, the spear had been heavily blunted. Yamamoto planned to perform another fighter sweep of the 16th, but reconnaissance flights failed to turn up adequate targets on New Guinea’s northeast coastline. 

On April the 17th, Yamamoto’s chief of staff, Vice-Admiral Ugaki Matome held a conference to review the lessons learned from their air offensive. The staff were reluctant to admit a startling and horrifying truth. Hundreds of aviators had been burnt to a crisp because the aircraft engineers messed up installing the protected fuel tanks. This led to countless aircraft catching fire from minor hits, even tracer rounds. When Japanese aircraft saw they were on fire, they assumed they had been scored a fatale hit from the enemy, though in most cases their aircraft were minorly damaged. Many of the pilots in these situations chose to kamikaze their aircraft.

Thus Operation I-Go was finished, but despite all the unrealistic exaggerated reports from the Japanese pilots, the entire operation only really amounted to setting back the American operations in the Solomons for about 10 days. While the Japanese believed they had inflicted tremendous damage, in reality the only real insignificance for the allies was to postpone some bombing raids and minelaying activity. The most significant consequence of operation I-Go would actually end up being Admiral Yamamoto’s decision to personally carry out a tour of the forward airbases, as he tried to raise morale for the men like he had done at Rabaual. This would have a very dire effect on the future of the Empire.

 

I would like to take this time to remind you all that this podcast is only made possible through the efforts of Kings and Generals over at Youtube. Please go subscribe to Kings and Generals over at Youtube and to continue helping us produce this content please check out www.patreon.com/kingsandgenerals. If you are still hungry after that, give my personal channel a look over at The Pacific War Channel at Youtube, it would mean a lot to me.

Operation I-Go was quite the lackluster offensive, despite what the Japanese pilots were claiming to their leadership. The leadership likewise believed the claims or were unwilling to see the truth of the matter. They had only accosted the allies about 10 days in the solomons.