I think the Doolittle Raid was necessary. I understand and can agree with the Coral Sea argument, but the boost in morale and "PR Stunt" was, IMO, a bit more than just that. Up until this point, the Japanese had been unbeatable. Heck, an entire army surrendered to them without much more than token resistance in ...Hong Kong? Singapore? (mind is a bit foggy this early in the mornin), and they'd been steamrolling through China and the Pacific for several years. The world looked at the newspaper headlines and read about another Japanese victory. The Japanese people read their propagandapapers and listened to Radio Tokyo and believed all of the stories about Divine Destiny (or whatever they called it, creating the Greater Southeast Asia CoProsperity Sphere). And then Doolittle comes buzzing along, tosses a few bombs on Tokyo, and putters on into China. Great military victory? Massive infrastructure damage? Crippling blow to production/training? Nope. A sudden and violent rupture of pre-existing views of Japanese superiority and invincibility, calling into question the unshakable faith and blind devotion to the reigning military mindset? Yep. The world, and especially the US and her Allies in the Pacific, realized that they had been paying too much attention to what Radio Tokyo had been saying about themselves, and began to believe that the Japanese could be hurt, beaten. Carlson's Raiders attacked an island being held by Japanese forces and killed a lot of the garrison there (we won't go into all that went wrong with that particular venture...yet...), but Doolittle attacked the Japanese Home Island itself. The world changed their views and began to look at the Japanese not as invincible, but as tough foes: a rough road ahead, but winnable.
::steps off soapbox, goes in search of early-morning caffeine::