The 14 April 1943 message schedule for C-in-C of the Combined Fleet Admiral Isuroku Yamamoto’s visit to Ballale and Buin was immediately recognized by Hypo traffic analysts and given to Marine Major Alva Lasswell, who worked on it most of the night. The first decrypt was hand carried by Commander W. Jasper Holmes to Layton, who immediately notified Nimitz. Nimitz passed the information to Halsey, who forwarded it to his subordinate air commanders. Further decrypts of this and a supplementary message were also made by navy stations. Rear Admiral Marc. A. Mitscher, Commander Air Solomons advised Halsey that Army Air Force P-38’s on Guadalcanal had the range to interdict Yamamoto’s flight. Halsey and Nimitz approved his recommendation. Early accounts that Washington, including Secretary Knox or Roosevelt, had to approve the shootdown attempt are unsubstantiated and have been discounted. Army Air Force Major John W. Mitchell’s 339th Fighter Squadron based at Fighter 2 on Guadalcanal intercepted the flight killing Yamamoto and all personnel in his plane, while Chief of Staff Matome Ugaki and Flight Petty Officer Hiroshi Hayashi survived in the second plane shot down. Initially, credit for shooting down Yamamoto was claimed and awarded to Captain Tom Lanphier. Later research shed considerable doubt on that conclusion and indicates Lieutenant Rex T. Barber may well have been the Army Air Force pilot that shot down Yamamoto.
Next came the
push up the Solomons to Munda, Vella Lavella and then to Empress Bay, Bouganville.
Here radio intelligence, Coastwatchers, and search planes of many varieties
all did their part. However, the growing superiority of the Allies
in the air, at sea, and on the ground left no doubt as to the outcome.
Radio intelligence generally became far more accurate and complete as its
ranks swelled. However, it was no longer quite as crucial as it was
in the earlier parts of the war like the invasion of Guadalcanal.
In referring to Guadalcanal, the official Marine Corps history comments
that “Seldom has an operation been begun under more disadvantageous circumstances.”