He was a aviation pioneer and a great American hero. One of his greatest technological accomplishments was in recognizing the importance of being able to fly with zero visibility and the development of instrument flying. But the thing for which he'll be remembered most was the Doolittle Raid -- the squad of B-25s launched from the carrier USS Hornet to drop bombs within Japan for the first time during WWII. The raid caused the Japanese to fortify their homeland defense and thus weaken their Pacific forces.
Happy Birthday General Doolittle!
Aside: An actor playing General Doolittle appeared in the 2001 movie, Pearl Harbor. That actor was Alec Baldwin, and Baldwin's convincing portrayal of a war hero like Jimmy Doolittle should be proof that Baldwin is a very talented actor.