Oikawa served as aide-de-camp to Crown Prince Hirohito from 1915 to 1922. That long association appears to have given him personal trust at court and helps explain his appointment to head the naval staff in 1944. One interpretation is that Hirohito was losing confidence in the Army and officers close to Hideki Tojo, and was gradually removing Tojo's supporters from the Navy. Trusted naval officers could give the emperor support if he needed to move against them. Oikawa's promotion to rear admiral by 1928 also shows how far he had advanced since his middling academy performance.
Notable Point · 3:40-5:15
Court access and rapid promotion
Service as Crown Prince Hirohito's aide-de-camp helps explain why Oikawa became a trusted senior officer during Japan's wartime crisis.