Targetarear:
"I've always found the 'conspiracy' argument RE the U.S. defenses at Pearl Harbor being in a low state of alertness, while the American aircraft carriers were away at sea (and hence undamaged by the bombing), to be rather compelling. Franklin Roosevelt was desperate to get the U.S.A. into the war in Europe, one way or another... --C.K."
This is reading history backwards. In 1941, the navies of the world still considered dreadnought battleships to be their most important vessels. Only Britain, the USA and Japan had aircraft carriers, and few believed they were anything more than escorts for the dreadnoughts. Carrier-borne aircraft were still in their infancy, and quite primitive when compared to land-based ones. With one exception, the torpedo bomber attack on the German battleship Bismarck, the only successful air attacks on dreadnoughts had been on those that were stationary on the high seas or at rest in their bases.
Actually, the Japanese Imperial Navy studied in depth the British Royal Navy's highly successful attack, via carrier-based torpedo-launching planes, against the Italian fleet in the naval base at Taranto on November 11, 1940, in which most of the Italian ships were either sunk or seriously damaged at a cost of only two aircraft to the British force.
To any navy that was paying attention, that one-sided victory--which should've been without surprise since Britain had been at war with Italy for five months--demonstrated the military value of aircraft carriers as a force of their own. The Japanese used the Taranto raid as the blueprint for their attack on Pearl Harbor just over a year later.
I'm guessing that the U.S. Navy wasn't oblivious to what had been demonstrated by the Royal Navy at Taranto either... --C.K.