Could the Japanese have invaded the US?

[D-Day_Dodger]

I would like to know what American military planners in WWII really thought about the possibility of a Japanese invasion of the West Coast Did they seriously think there was a real threat of this happening? If so, why?

I, for one, can't imagine anyone taking the idea seriously, considering the difficulties involved. Even assuming they could have gotten an invasion force to the West Coast and landed them without incident, their troubles would have been just beginning.

To supply their Army and Navy would have been nie on impossible considering they would have had to trace a tenuous supply line thousands of miles long across the Pacific, which would have been subject to interdiction by every submarine and surface craft available to the US and Canada on the West Coast or at the Hawaiian Islands. Likewise for the air power of the US Navy and Air Forces.

Any invasion fleet off the American coast would have been ravaged by unending attacks from land based aircraft and would have been unable to easily replace it's losses, especially in carriers and carrier based aircraft, while the Americans could send planes straight from the factory into the battle (a la Stalingrad). Even if the Japanese had managed to capture the Hawaiian Islands, while easing their supply problems, this would not have had much effect on the decisive battles being fought further east.

As for the invading armies, what would their objectives have been? Conquest? Hardly. How do you conquer a country the size of the USA? Perhaps a large scale raid designed to destroy American factories and port facilities? But no matter how successful these limited objectives might have been, the cost would have been the ultimate elimination of the invasion force which would have withered and died on the vine from lack of supply and casualties.

A Japanese attack on the United States would have been a suicidal Banzai charge of monumental proportions. It would have been the turning point in the war, but certainly not in the way the invader envisioned.

So, back to my original question. How did the military planners view the likelihood of attack? I'm willing to bet that they had contingency plans made up, maybe even years before the war with Japan started. But armies draw up contingency plans for the most unlikely of circumstances. Heck, even the Canadian Army in the 30's, for training purposes, drew up a war plan for attacking the USA (success for this plan depended on surprise - therefore we would attack at night!).

I'm curious to know what thoughts others have on this subject. Cheers.