Conceived in January 1942 in the wake of the devastating Japanese surprise attack on Pearl Harbor, the “joint Army-Navy bombing project” was to bomb Japanese industrial centers, to inflict both “material and psychological” damage upon the enemy. Planners hoped that the former would include the destruction of specific targets “with ensuing confusion and retardation of production.” Those who planned the attacks on the Japanese homeland hoped to induce the enemy to recall “combat equipment from other theaters for home defense,” and incite a “fear complex in Japan.” Additionally, it was hoped that the prosecution of the raid would improve the United States’ relationships with its allies and receive a “favorable reaction [on the part] of the American people.”

Originally, the concept called for the use of U.S. Army Air Force bombers to be launched from, and recovered by, an aircraft carrier. Research disclosed the North American B-25 Mitchell to be “best suited to the purpose,” the Martin B-26 Marauder possessing unsuitable handling characteristics and the Douglas B-23 Dragon having too great a wingspan to be comfortably operated from a carrier deck. Tests off the aircraft carrier Hornet (CV-8) off Norfolk, and ashore at Norfolk soon proved that while a B-25 could take off with comparative ease, “landing back on again would be extremely difficult.”

The attack planners decided upon a carrier transporting the B-25s to a point east of Tokyo, whereupon she would launch one pathfinder to proceed ahead and drop incendiaries to blaze a trail for the other bombers that would follow. The planes would then proceed to either the east coast of China or to Vladivostok in the Soviet Union. However, Soviet reluctance to allow the use of Vladivostok as a terminus and the Stalin regime’s unwillingness to provoke Japan compelled the selection of Chinese landing sites. At a secret conference at San Francisco, Lieutenant Colonel James H. Doolittle, USAAF, who would lead the attack personally, met with Vice Admiral William F. Halsey, Jr., who would command the task force that would take Doolittle’s aircraft to the very gates of the empire. They agreed upon a launch point some 600 miles due east from Tokyo, but, if discovered, Task Force 16 (TF-16) would launch planes at that point and retire.

Twenty-four planes drawn from the 17th Bombardment Group, USAAF, were prepared for the mission, with additional fuel tanks installed and “certain unnecessary equipment” removed. Intensive training began in early March 1942 with crews who had volunteered for a mission that would be “extremely hazardous, would require a high degree of skill and would be of great value to our defense effort.” Crews practiced intensive cross-country flying, night flying, and navigation, as well as “low altitude approaches to bombing targets, rapid bombing and evasive action.”

Lieutenant Henry L. Miller, USN, oversaw the carrier take-off practice at Eglin Field, Florida, work that elicited praise from Doolittle for Miller’s “tact, skill and devotion to duty.” With everything not deemed essential stripped from the planes, Hornet loaded 16 B-25s (all that could be shipped) on board at Alameda (31 March–1 April 1942) and sailed to rendezvous with the carrier Enterprise (CV-6) to form part of Halsey’s TF-16.