Here’s my two cents on the “Hawaiian Invasion” question...the Japanese would invade, to what end?
As in, why would they want to?
The Japanese Army’s running wild across East Asia in 1941-2 was geared primarily towards one thing...seizing strategic resources. They wanted the oil of the Dutch East Indies, and the rubber, tin etc. of Indochina and Malaysia. Food was certainly useful, but I don’t think it was as vital; they could plunder plenty of that from China, Korea and Manchuria. (Food from conquered lands was valuable primarily in terms of trade for finished goods from Japan’s industries.)
Outside of the Indies, Indochina and Malaya, most of the other land they grabbed was for strategic reasons more than anything else. Burma and Thailand constituted a rearguard protection of Indochina against invasion from India and cutting Allied supply routes to China, and the Philippines were a strategic defense of Japan’s primary supply routes north and south (which straddled the PI). The Army’s forays into the Central Pacific and Southwest Pacific islands (which again netted the Japanese nothing resource-wise) mostly was due to the demands of the Navy...partly because of the Navy’s expectation of the great Mahanian “decisive battle” in the central Pacific, but mostly because the Japanese Navy (rival in all but name to the Army) was petulantly saying “we can play conqueror too!”.
Time has to be considered as well...the Japanese knew that they would only have X amount of time to grab what they were after, before they expected the threat of an orchestrated reprisal from the United States and Britain. The amounts of time allocated to each Army commander to achieve their objectives was not great. General Masaharu Homma, who was actually one of Japan’s best generals, was allotted only fifty days for his assigned conquest of the Philippines. (When that took four months and additional troops pried away from China and Java to complete, Homma’s career was ruined.)
To make such rapid conquests possible, the Japanese had spent years on spying and reconnoitering their intended targets. Their landing forces were dependent on long stretches of poorly defended beachfront, lots of ground intel, and encountering unprepared or ill-trained colonial forces and unmotivated Western regulars caught off guard...neither the Japanese Army or Navy had anything approaching an actual doctrine of amphibious-warfare-under-fire a la the US Marines. Also, the supply lines involved were fairly short.
With Hawaii (and, frankly, with Midway too), the Japanese were looking at a hard target that offered nothing for the effort. They did not have the intel of on-the-ground conditions in 1942 to plan an invasion, they were facing the ultimate citadel of motivated, alert, mad-as-hell Army, Navy and Marine forces, who had nowhere to retreat to (and so would have stood and died fighting), and did not have a serious plan for landing forces in the face of concentrated resistance. And even if they could have taken it...what good would it have done them? It offered nothing of consequence in the way of resources...what there was wouldn’t have been worth the shipping. Indeed they would have had to supply a garrison on Hawaii, and that would have stretched the limit of their supply lines in submarine-infested waters.
In a nutshell, Hawaii wasn’t worth the effort to invade, and the Japanese knew it. They considered it worth threatening for strategic reasons (again geared towards drawing the Allied naval forces out for the great “decisive battle”), but that was all. In the brief time the Japanese knew they had to grab territory and resources, there were far more important pickings to be had.
A major H/T to Jon Parshall and his website, www.combinedfleet.com, for his and his associates’ extensive study of this and many other deep questions of the Japanese side of the war.
Not only its own garrison - Japan would have to find a way to keep several hundred thousand Hawaiians fed and watered, too. It would've been sheer idiocy to try to take Hawaii.