On April 18, 1942, Doolittle and his flyers were hours away from takeoff when general quarters sounded. The fleet had run into the picket ships some 600 miles away from the Japanese coast. A fishing boat was quickly sunk, but fearing surprise was lost, the bombers were launched.
Doolittle took off first. The bombers had to use the power of their engines to pull enough air over the wings to take off. He cleared the bow by several feet, and led his aircraft aloft. The fleet turned and ran for Hawaii.
The B-25 was a tactical bomber, with little defensive armament except for its speed. They had little to fear, since the primary target, Tokyo, was undergoing air raid drill and it was assumed the incoming planes were part of the test. They dropped their bombs on factories, military targets, and one bomb fell inside the Imperial Palace.
Flying on to China, all of the bombers crashed at the extreme range of their fuel, never joining the Chinese Air forces. Doolittle thought his mission was a failure because he wasn't able to deliver any of the bombers. Chiang Kai-Shek, who was kept in the dark fearing leaks in his security, never alerted his forces to support the bombers landing.
When Doolittle got back to the United States, he was unprepared for the greeting he received. He was the first genuine hero, and he was acclaimed wherever he went. He became a commander in the European Theater of Operations. Eight of Doolittle's flyers were executed after the Japanese captured them.
For the Japanese, the idea that the enemy could bomb Tokyo, bomb the Imperial Palace, sent shock waves through the War Cabinet and the Imperial High Command. Fighter groups were recalled from abroad for home defense.
If the High Command had any idea of how Doolittle's raid were the first of thousands of sorties to come to Japan, they would have begun building defenses much earlier. But it was not until late 1943, when the Allies began to acquire bases close enough to Japan to attack by air, that regular air raid drills were practiced.