<p>The immediate objective was to hit Japan somehow, somewhere. From a number of sketchy concepts emerged the idea of an AAF bombing raid against the home islands, launched from a Navy carrier offshore and recovered in mainland China.
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<p>Captain Francis S. Low, a Navy submariner on Admiral Ernest J. King's staff, gets credit for the basic plan: he thought that Army B-25s or B-26s could be flown off a navy carrier and directed against Japan. Navy Captain Donald B. Duncan, King's air operations officer, did the analysis, chose the <hi format=ital>Hornet</hi> as the carrier, laid out a plan of action, and suggested that modified North American B-25 medium bombers be used. Arnold agreed, and asked Lieutenant Colonel James J. Doolittle to oversee the modifications and train the crews.
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<p>The strike was planned as one part of a five-part operation that would eventually establish the Tenth Air Force in Burma. The B-25s would go on strength with the Tenth Air Force after their successful recovery in China.
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<p>Doolittle drew the aircraft and crews from the 34th, 37th and 95th Bombardment Squadrons of the 17th Bombardment Group (Medium), and from the 89th Reconnaissance Squadron. They trained at Eglin Field, FL, learning how to snatch the B-25s off the ground at lift-off speeds far below the ones that had been drummed into their heads during transition to the type. Late in March 1942, they left Eglin for McClellan Field, CA, for a final inspection of their fleet by technicians at the Sacramento Air Depot. On 31 March they made the short flight to the Naval Air Station at Alameda, watched their B-25s loaded aboard a carrier, and sailed with the task force when it left on 2 April.
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<p>Doolittle's planes—the mission was his also, after he had volunteered himself to Arnold—had been modified with long-range fuel tanks, reduced armament and the addition of black-painted broomsticks masquerading as tail guns in the hope of fooling Japanese fighters, at least on the first pass. They were loaded with three 500-lb (227-kg) demolition bombs, and one 500-lb (227-kg) incendiary cluster, and their assigned targets were in Tokyo, Yokohama, Nagoya, Osaka and Kobe.
