The attack by American bombers on the heart of the Japanese Empire in April 1942, commonly known as the „Doolittle-Raid“, probably stands out as the most strategically significant air attack during all of World War II.
The idea of an attack on Tokyo originated in the office of ComInCh/CNO Admiral Ernest J. King in Washington D.C., who realized the miniscule amount of deception which had come out of the early carrier raids of February and March. A raid on the home islands, however, would have the desired effect of slowing down Japan’s East Asian operations.
The question remained, however, how such an assault could be mounted. The short-ranged U.S. carrier planes and the time required to launch and land them ruled out their use. It was Captain Francis S. Low, from CNO’s Operations Section, who suggested the use of Army B-25 Mitchell light bombers – these planes, too large to be landed back aboard a carrier, would have to fly on to China and land on Allied airfields there. King agreed to the idea; the brand-new carrier Hornet, under Captain Marc A. Mitscher, undertook flying-off tests with these bombers in February, while on the beach, volunteers were training the take-off from short distances. Colonel Jimmy H. Doolittle would lead the attack.
Hornet reached Alameda, near San Francisco, on April 1, 1942, and took aboard the squadron of B-25 bombers, sixteen total, to leave the next day for the North Pacific, there to rendezvous with Vice-Admiral William F. Halsey’s support elements, carrier Enterprise and escorts. These vessels left Pearl Harbor on April 8, totaling a carrier, two cruisers, and four destroyers, and met with Hornet and her similar-sized escort on the morning of April 13. Enterprise would conduct the regular air patrols and searches, since Hornet’s deck was full with the bombers.
After fueling from two fleet oilers, Halsey took his four cruisers and two carriers and dashed towards Japan. The destroyers remained back, too much of a hindrance on the high-speed run Halsey was conducting.
On the morning of April 18,  everything having gone according to plan until this time, problems loomed ahead. Hornet’s lookouts had sighted a small trawler dead ahead. The Americans had hit the Japanese picket line.
Halsey reacted quickly: cruiser Nashville was detailed to sink this target; the combat air patrol from Enterprise took on this and a number of other trawlers now appearing to litter the sea around the Task Force. Halsey ordered Captain Mitscher to launch his planes at once. He accepted 250 further miles for the B-25 to fly, but there was no other choice now.
The launch having succeeded Halsey hurried back east at 25 knots to escape the alarmed Japanese. The attack, however, was a success: without notable resistance, the planes found their targets, damaged industrial complexes and a carrier in drydock,  Ryuho (under conversion from a submarine tender), and headed off to the Chinese mainland. Nine aviators were captured by the Japanese, four were executed.
The material damage incurred by the Japanese was minor; but the effect of it on both American and Japanese morale was immense. The Japanese had to admit that their idea of a restricted war whose scope could be controlled by Japan was faulty. Their fabled perimeter defense clearly had gaps. And the Japanese progress in the Indian Ocean became secondary to the destruction of the American carriers.
The situation was clear to Admiral Yamamoto Isoruku. With the aid of his assembled fleet he would force to Americans into battle and destroy them. Nothing, nothing at all, would now get in his way of putting through his Midway plans. So focused on Midway he allowed the Americans to blunt the Japanese thrust towards Australia in the Coral Sea.
Alas, only the Midway operation itself would show how much Yamamoto had succeeded in his aims.