The success of the torpedo attack on Taranto by the British on 11 November 1940 was of great interest to the Japanese. One problem was that Japanese Model II torpedoes were designed to run at a depth of about 65 feet (20m), deeper than the waters of Pearl Harbor at 50 feet. The difficulty was overcome by adding wooden fins which gave not only more stability, but also greater buoyancy. The running depth was reduced to 40 feet (12m). Intensive training with the Nakajima B5N2 Kate aircraft increased accuracy from 18% to 70% on moving targets and even better figures on stationary ships. Admiral James O. Richardson (Richardson, James O.) had discounted the need for anti-torpedo nets and Japanese espionage reported their continuing absence in a message sent by Takeo Yoshikawa (Yoshikawa, Takeo) on 2 December.