Before his death Yamamoto had implemented a new strategy, codenamed Operation I-GO. The Battles of Guadalcanal and Buna-Gona-Sanananda were heavy setbacks to his plans to expand the perimeter of the Japanese Empire to the east of Australia so as to throttle the supply routes to MacArthur’s Allied armies. A complete strategic rethink was required. The conclusion that Yamamoto reached was that expansionist new strategies were no longer possible. In the South Pacific, as in the Central Pacific, the United States would have to be drawn into a war of attrition so difficult and bloody that they would have to sue for peace on terms favorable for Japan. Japan’s war of aggressive expansion would now become a war of aggressive defense. In the South Pacific the new strategy would be dependent on air defense—using his bombers to try to disrupt Halsey from building airfields. In April Yamamoto had moved his HQ to Rabaul to oversee Operation I-GO. It was a decision that doomed him. When Watanabe complained that the information about Yamamoto’s visit to Ballalae Airfield should be done by courier and not by radio, the communications officer replied, “This code only went into effect on 1 April and cannot be broken.”
Yamamoto accurately anticipated that the Allied advance in the Solomons and New Guinea would focus on subjugation of the Japanese stronghold at Rabaul. Apart from one small but important twist, namely the eventual decision to isolate rather than destroy Rabaul, Yamamoto’s understanding of the Allies’ plan proved completely accurate.
Within five days of the Battle of Guadalcanal being officially declared as over on 9 February 1942, Lieutenant-General Kenney authorized a plan to “really take Rabaul apart.” This started on the night of 14–15 February with a bombing raid by thirteen B-17 Flying-Fortress bombers from the 63rd Bomb Squadron. Munitions and fuel dumps were targeted. A second wave of ten bombers from 65th Bomb Squadron dropped incendiaries on downtown Rabaul. Two more waves consisted of eight B-17s and four Liberators. There were no fighter interceptions. Japan’s failure to regain Guadalcanal was thus quickly brought home. Petty Officer Igarashi at Vunakanau Airfield noted that after the bombing, he “felt beaten physically and emotionally.”
Yamamoto had further predicted the double-pronged Allied advance through New Guinea and the northern Solomon Islands. He therefore set up the ‘ring of airfields’ around Rabaul that would determine the outcome of the battle ahead. His inspection visit to Ballalae Airfield, the cause of his death, was a key indication of the importance he now placed on these ‘ring’ airfields. The result was, “Most combat took place inside or very close to a triangle with Port Moresby at the western point, Guadalcanal at the eastern point, and Rabaul at the northern apex.”
He knew that US forces would advance under the cover of air superiority, which in turn depended on their ability to build forward airfields. In anticipation, Yamamoto ordered a massive build-up of bombers and fighters with the aim of preventing US supply of matériel for the building and equipping of their advance airfields. The battle for Henderson Field on Guadalcanal was the first of these contests and Yamamoto was sure that others would follow. What he hoped was that the shorter lines of supply from airfields closer to Rabaul would give him the advantage over US forces. Contrary to the reports coming back from his pilots indicating that great air victories were being won against US forces in the Solomon Islands, his tour of inspection was beginning to reveal the opposite. One of the things that he would surely have noticed on his tour of the new airfields built to defend Rabaul was that by comparison with the US airfields, they were poorly constructed. As early as 25 October 1942, Rear-Admiral Ugaki had noted in his diary, “every time it rained heavily, about ten planes were damaged due to skidding.” The arms race to build new, bigger and better airfields would be won ‘hands down’ by the US Seabees.
Just as Yamamoto used the post-Guadalcanal lull to bolster his defenses for the anticipated battle ahead, Halsey prepared his forces for the next stage of the advance in the central and northern Solomons. A firm advocate of unity of command, he oversaw the realignment of air command that had inevitably been confused given the presence of the US Army’s Thirteenth Air Force led by Major-General Twining, the Marine Air Corps as well as the New Zealanders who had by now arrived with their Curtiss P-40 Warhawk squadrons and Lockheed Hudson search planes. As well as different services and nationalities, there was a profusion of new equipment; in addition to Warhawks, fighters included the Lockheed P-38 Lightning, Chance Vought F4U Corsair, Bell Airacobra as well as the new Grumman F6F Hellcat, an updated replacement for their Wildcats, which were still the US Navy’s mainstay. Bombers consisted of Boeing B-17 Flying Fortresses, Consolidated B-24 Liberators, Dauntless Helldivers, General Motors’ Grumman Avengers and North American B-25 Mitchells.
For this extraordinarily diverse force’s operational control devolved to COMAIRSOL, the lugubrious acronym for Commander of Air Forces in the Solomons. A solution to the intricacies of command and responsibility between Lieutenant-General Millard Harmon, Deputy Commander of air forces of the South Pacific Area and Rear-Admiral Aubrey Fitch, who commanded the US Navy and Marine Air Forces in the Solomons, was achieved under Vice-Admiral Halsey’s directive that there must be a unified command. Broadly it was agreed that combat command should be vested in the respective services with minimal disruption of normal command channels by COMAIRSOL whose role was largely one of strategy and coordination. Surprisingly, the diffuse system of command adopted avoided most of the ‘political’ pitfalls and worked extremely effectively.
At Guadalcanal there was a concomitant build-up of airfield capacity to take the fighter squadrons. Four new airbases were constructed as well as vast storage facilities to cope with a huge build-up of munitions, gasoline, clothing and food that was brought in to prepare for the campaign ahead. During March 1943 Allied bombers made sporadic attacks on Japanese airfields on Ballalae, Kahili, Shortland Island and Munda on the northwest coast of New Georgia. In addition a reconnaissance picture was built of Japanese movements, airfields and installations. When photographs revealed the development of a Japanese seaplane base off southern Bougainville, a dawn fighter attack was ordered on 28 March. Led by Captain Lanphier of 70th Squadron, six P-38s destroyed eight Japanese seaplanes. Rex Barber of 339th Squadron, later Lanphier’s confederate in the slaying of Yamamoto, was lucky to survive the attack when he hit the mast of a Japanese ship and lost three feet of wing. At the end of the month however, even with these kills included, only 16 Japanese planes were shot down. As for the Allies, there was not a single loss recorded in the Solomon Islands.
It was to be a brief lacuna in the Solomons campaign. At the beginning of April the Japanese returned in force as Yamamoto’s I-GO campaign started in earnest. The channel between Tulagi and Guadalcanal hummed with the to-and-fro of US troop transports, merchantmen, tenders and warships. It was an irresistible target. On 1 April, Japanese bombers, escorted by Zeros, were launched in a mass attack on US assets at Guadalcanal. They were met with an assortment of forty-two Allied fighters. After a three hour dogfight twenty Zeros had been shot down versus six planes of Fighter Command.
After a week of sporadic bombing attacks by both sides, Allied watchers on the coast of New Guinea indicated that a major attack was imminent. In total 160 Japanese aircraft were headed down the ‘Slot.’ All seventy-six Allied fighters were put in the air. Thirty-nine Japanese planes were downed against seven scored in return. Only Major Walden Williams of 70th Fighter Squadron was killed as the US had by now developed a sophisticated and rapid pilot rescue service for pilots dunked in the sea. Brigadier-General Nathan Twining, commander of the Thirteenth Air Force had himself been rescued from the sea by the US Navy in early February after six days spent in rafts with fourteen colleagues after their plane had been forced to ditch on its way from Guadalcanal to the US Air Force HQ at Espiritu Santo.
Yamamoto also launched mass attacks on US airfields on New Guinea. On 12 April 1943, just six days before Yamamoto’s assassination, Mitsubishi G4M1 ‘Bettys’ took off from Vunakanau Airfield near Rabaul. They were accompanied by 130 Navy Zeros along with 65 Zeros from the carriers Zuikaku, Hiyo and Junyo. They were headed for Milne Bay and all US fighters were scrambled to meet them. US defenses were sold a dummy. The Japanese attack switched course and was only picked up as it was crossing the Owen Stanley Mountains headed for Port Moresby. Kenney was on hand to witness a mêlée involving over a hundred aircraft. Kenney noted that the Japanese “came into sight of my headquarters at 10.23 a.m. Forty-five bombers in one beautifully flown mass formation … while above them between 60 and 70 fighters for protection.” Ten Japanese aircraft including two fighters were shot down. It was the 106th air raid on Port Moresby and the largest to date.
The expected raid on Milne Bay the following day, 13 April, did not materialize. But on 14 April Yamamoto waved off the last attack of Operation I-GO. Twenty-three ‘Val’ bombers and 44 ‘Bettys’ were accompanied by 129 Zeros from the 11th Air Fleet and the Third Fleet. Only three ships at Milne Bay took hits and none were sunk. Japanese claims were exorbitant: three large and one medium transport sunk, six transport heavily damaged and forty-four Allied aircraft shot down. In reality only one P-40 Warhawk was lost and the defenders claimed nineteen confirmed kills. In the battle Lieutenant Richard Bong, who was described by Kenney as “a little blonde-haired Norwegian boy” started to make a name for himself with the double shooting of ‘Betty’ bombers. Kenney, who liked heroes and their legends, told his staff to “watch for that boy Bong.” In the combined reports coming from I-GO, the Japanese claimed a massive victory in which their bomber units had supposedly sunk a cruiser, two destroyers, six cargo ships, ten medium cargo ships as well as shooting down 134 Allied planes and damaging fifty-six more. Emperor Hirohito was impressed. “Please convey my satisfaction to the Commander in Chief, Combined Fleet, and tell him to enlarge the war result more than ever.”
By contrast, Kenney was damning about the use and effectiveness of Japan’s Air Force: “… the way he [Yamamoto] had failed to take advantage of his superiority in numbers and position since the first couple of months of the war was a disgrace to the airman’s profession.” Apart from the rare exception of mass attacks, Japanese attacks were marked by their use of aircraft in ‘penny-packets.’ Kenney was probably not aware that the inability of the Japanese Navy Air Force to launch sustained heavy bombing was in large part due to their logistical weaknesses including lack of experienced aviation engineers, ground crews, adequate airfield facilities and airfield equipment.
By the end of May however, US morale was rising. Apart from killing Admiral Yamamoto, the Allies had been significantly reinforced over the month. Twining was now able to rotate his pilots to allow them time for rest and recuperation (R&R). The contrast with the Japanese Air Force’s ‘fight-till-you-die’ policy could not have been starker. Essentially for Emperor Hirohito and the Japanese high command, serving pilots, as with their ground troops, were expendable commodities—used until they were either wounded or died.
Guadalcanal now served as the US rest and recuperation (R&R) base for the Solomon Islands Campaign and here resting pilots could also be put to use instructing fresh arrivals. The main problem facing the US Army Air Force at Guadalcanal was the lack of airfield construction to enable satisfactory dispersal of the 300-plus aircraft that had arrived on the island in the early summer of 1943. After ‘Hap’ Arnold complained to Vice-Admiral ‘Bull’ Halsey, new areas for dispersal were organized. Through the spring and early summer the build-up in resources at Guadalcanal allowed a steady increase in bomber action against Bougainville in night attacks. Daylight attacks by Japanese fighters coming down the ‘Slot’ also became a daily feature. Costs to Japan duly increased. In a dogfight on 13 May, the Japanese lost sixteen fighters. Towards the end of May, it seemed that Japanese attacks were losing strength. By comparison Allied attacks on southern Bougainville were increasing as Curtiss SB2C Helldivers, newly equipped with fifty-gallon auxiliary tanks, extended their operational range.
Nonetheless, by the beginning of June it was clear from reconnaissance that with 225 aircraft assembled at their airfields and some fifty ships in the harbor, Japanese forces at Rabaul were building resources for a major new effort. Nevertheless fighter exchanges remained heavily in favor of the Allies. On 7 June, a major Japanese effort ended with twenty-three of their planes downed against nine Allied aircraft. Apart from the disparity in aircraft losses, the key difference was that all the Allied pilots were rescued while all of the Japanese were assumed to have died. The 12 June air battle was even more one-sided; the Allies scoring thirty-one kills to six losses and two pilots killed. Still, in the short term, the Japanese well of resources appeared undiminished.