Did the Japanese have the ability to conduct raids on our West Coast, and more importantly, did U.S. policy-makers believe that they did?
This is a complicated issue and I won't be able to cover everything in this post.
It is said that amateurs discuss strategy, pros discuss logistics. While perhaps overstated, this aphorism does have much truth in it, for the question of whether Japan could have conducted raids along our coast depends on an answer to this question.
Many at the time seemed to believe that actual invasion by troops was a possiblilty. The facts are that it would have been just about impossible for Japan to have carried this out. Let's briefly go over some principles for amphibious attacks.
The general rule is that the larger the invasion force, the closer (to the target) one needs their jump-off base. In other words, you can travel a long way with a small invasion force, but only a short distance with a large one. We needed a huge force to attack Normandy, and it was assembled in Britain, only a few short miles away. No way this force could have traveled from the U.S., for example. Likewise, the entire rational for our invasion of Okinawa in 1945 was to secure a base for the invasion of Japan proper. We could not have sailed the necessary fleet from our bases in the Marianas, for example.
Likewise, the various U.S. invasions of islands in the Pacific (Iwo Jima, Guadalcanal, Tarawa, etc) were relatively small-scale affairs, at least when compared to D-Day in Normandy, or to a possible invasion of Japan proper. Therefore we could sail our invasion fleet for some distance before attacking.
Most of this was known at least in theory during the initial days of the war. Even with a jump-off point of Hawaii it is hard to see how the Japanese could have invaded the continental U.S. However, there was much "concern: (really bordering on hysteria) in the country following Pearl Harbor, even among otherwise sober policy makers. Some of them can therefore be forgiven for imagining that Japanese troops might land on our beaches.
As for coastal raids, that is another matter. In order to have carries out these raids the Japanese would have needed to occupy Pearl Harbor. The object of their December 7 attack was not to do this, but to simply cripple our fleet so they could take over the western Pacific, which they did over the course of the next six months. They did not invade Hawaii at the time because they lacked the logistical capability to do so, and because the US still had substantial forces in the western Pacific.
http://theredhunter.com/2005/02/was_a_j … ssible.php
