Genda understood the potential of massed air raids launched from multiple aircraft carriers steaming together.

An air power advocate from the time he attended the Japanese Naval Academy, Genda urged Japan's pre-war military leaders to stop building battleships (which he believed would be better used as "piers" or scrap iron) and concentrate on aircraft carriers, submarines, and supporting fast cruisers and destroyers.

Yamamoto ordered a number of officers to study Pearl Harbor and to draw up an operational plan.

His assessment of the Royal Air Force (RAF), Hawker Hurricane Mk I and Supermarine Spitfire Mk I fighters against the German Messerschmitt Bf 109E "Emil" later provided evidence that the Japanese Mitsubishi A6M Zero Model 21 could easily outmaneuver these Western European aircraft.

The carefully recorded details were secretly documented during his brief tour in London and were hand-carried by Genda during his return trip to Japan for naval department studies.

Genda's Western European trip provided added stimulus for Japanese strategic naval studies and exercises to discover weaknesses and formulate tactics that were later used against the U.S. On his return to Japan, he was assigned to the First Carrier Division and met with Yamamoto in early February 1941, during which time Yamamoto presented some ideas for attacking the U.S. Pacific Fleet.

[6] Genda had previously considered an attack on Pearl Harbor in 1934 and had discussed the possibility then with Takijirō Onishi.

[11] In the four months after the attack, the Imperial Japanese carrier units ranged across the Pacific and Indian oceans causing major damage to Allied forces and bases.

He personally felt that the Kawanishi N1K2-J Shiden-Kai (Allied code name, "George") was equal to the American F6F Hellcat and F4U Corsair.

"[13] Genda documented his World War II experiences in a revealing autobiography, published in Japan.

"[14] With the surrender of Japan and subsequent dissolution of the Imperial Japanese Navy, Genda went into private business.

[15][16] As commander of the Air Self-Defense Force, Genda successfully pushed for the acquisition of the F-104 Starfighter, of which Japan bought 230.

He remained influential in politics for more than 20 years, as a leading member of the Defense Division of the LDP's Policy Affairs Research Council, often representing the hardline nationalist position advocating abrogation or curtailment of Article 9 of the postwar Japanese Constitution and open remilitarization of the armed forces.

During a speaking engagement in the U.S. in 1969, in response to a question from the audience, he said that he thought the Japanese would have used the atomic bomb if they had had it; in the resultant uproar in Japan he was forced to resign as chief of the defense policy board of the LDP, although he kept his seat in the legislature.