U.S. Naval Intelligence and the Imperial Japanese Fleet during the Washington Treaty Era, c.1922-36
Following the Washington naval arms limitation agreement of 1922 intelligence on the Imperial Japanese Navy became a top US priority. The limited intelligence sources available to the Office of Naval Intelligence (ONI) and the range and assessment of information obtained are discussed. The ONI’s assessment is discussed in detail showing an overall underestimate of Japanese strength despite their development of a formidable fleet. Navy Department officials did not share this view and final analysis indicated a gap between U.S. and Japanese strength leading Congress to authorise a massive building programme in 1934. It is concluded that intelligence assessment was rational but hindered by lack of reliable information.