Japan needed to regain the initiative after the losses of Guadalcanal and eastern New Guinea and the defeat in the Bismarck Sea. It was painfully obvious to the Imperial General Staff that the Allies were attempting to neutralize the critical Japanese base at Rabaul by island hopping up the Solomon chain to New Georgia.
Throughout early April 1943, Japanese Army and Navy conducted Operation I-Go from bases in the northern Solomon Islands to counter the Allied build up. The plan was developed over the month of March by Japan’s master strategist and architect of the Attack on Pearl Harbor, Admiral Isoroku Yamamoto. I-Go was a massive joint aerial offensive against Allied shipping and airfields that was to prevent further Allied landings in the Solomon Islands. It was exceptionally successful in severely damaging Allied logistics infrastructure and much needed shipping, which significantly delayed Allied preparations. However, without any amphibious operations to retake Guadalcanal and the southern Solomons, I-Go would ultimately not stop any operations.
On 14 April, Adm Yamamoto’s staff began preparations for him to visit outlying fighter squadrons in order to congratulate them on a job well done. However the Americans knew the exact times and routes of Yamamoto’s movements because American code breakers deciphered the radio transmissions. Japanese army intelligence suspected the navy’s code was compromised, but the “Divide and Conquer” method of governance by Japan’s totalitarian and militaristic system precluded them from warning the Japanese Navy. Moreover, Japanese commanders in the area were worried about these visits but they didn’t want to lose face caused by any perceptions that they couldn’t protect Yamamoto. Yamamoto himself knew the mission was too dangerous, but refused to lose face in the eyes of the pilots who were already told to expect him.
Over the next two days (!?!?!), a miraculous and singular, never-to-be-repeated episode of US government operational security and efficiency happened when the entire American chain of command up to FDR was briefed, and approved Operation Vengeance to assassinate Yamamoto. On the morning of 18 April 1943, 18 US Army P-38 “Lightning” fighters, with drop tanks for extended range, took off from the new Kukum Field on Guadalcanal and intercepted Yamamoto over the island of Bougainville. That the P-38s intercepted Yamamoto’s aircraft is a testament to the Lightning pilots’ skills in navigation (helped by Yamamoto’s legendary punctuality). Adm Marc Mitscher, (We will hear his name again) the air commander in the South Pacific, commented that, “It’s a thousand-to-one that they even see him.”
Yamamoto was in a G4M2 “Betty” bomber and had six “Zero” fighters for an escort. Another Betty carried the rest of his staff. In the ensuing dogfight, both of the bombers were shot down, killing everyone on board both aircraft. Adm Yamamoto was Japan’s best naval strategist, but more importantly he was the only officer in the Japanese military with sufficient respect to force coordination between the near violently rivaled Japanese Army and Japanese Navy. The Japanese would not be able to successfully coordinate a joint Army/Navy operation for the rest of the war.