@variance:
Of the 5 objectives I gave, which ones were most seriously on the table for Japan in the war?Â
I’d rank them in two groups and in the following order, from most to least likely (which is only a very rough estimate, given that many variables would have affected Japan’s chances of success if it had tried for these objectives).
Group 1: Achievable
a) More islands in the Pacific. I don’t have an opinion on the stated number of 20, but Japan could certainly have captured more islands (especially small ones in the Central Pacific) than it actually did. I’ve already mentioned the Ellice Islands, and Johnston would be another possibility. Note, by the way, that Johnston Atoll was astride the direct air route between the continental US and Australia, so its position had potential strategic implications if Japan had managed to capture it, given that the US basically used Australia as a staging area for its campaign in the Southwest Pacific. The capture of Midway would also have been quite within Japan’s capabilities if Spruance and Fletcher hadn’t ruined things for them. Midway was regarded as a strategic “keyhole” giving the US access to the Central Pacific, and after the Doolittle Raid the Japanese were eager to plug it. Midway might also have been handy in supporting an invasion of Hawaii…but maybe not in a major way, since I don’t think it had an anchorage.
b) Parts of India – specifically Ceylon, which Japan raided in 1942, and about whose security the Royal Navy had serious doubts. The RN established a secret naval base in Addu Atoll for precisely that reason. But India as a whole was simply too big and too populous for Japan to conquer; it contributed about 2 million troops to the Allied war effort.
By the way, as a variant on a) and b), one intriguing hypothetical Japanese objective about which Britain was worried was Vichy-occupied Madagascar, in the Indian Ocean. Britain (and the Free French, I think) invaded Madagascar in 1942 to preclude such a possibility.
Group 2: Not achievable
c) Australia. I think that, at best, the Japanese might have captured Darwin, which was the nearest part of Australia to New Guinea and which had an isolated position on the other side of the country from the most populated part of Australia. Japan actually air-raided Darwin at one point. But capturing Darwin would have been of dubious practical value. And capturing NSW would have been, I think, quite out of the question: too far away, too big, and too well defended.
d) China. Capturing a few more parts of it is credible, but capturing all of it isn’t. James Dunnigan addresses this topic in the section called “The War (A Big One) In China” in his book Victory at Sea. China was a disunited, non-industrial country, yet Japan only managed to capture parts of it during the four years (1937-1941) when China had its undivided attention. It didn’t get much further during the 1942-1944 period. And when Japan, out of desperation, eventually started committing elements of its powerful Manchuria-based Kwantung Army to the war in the Pacific, Japan’s position in China was seriously weakened. The Russians and the Mongolians, as I recall, made rapid progress there when they eventually attacked in August 1945.
e) The US West Coast. Even if a hypothetical Japanese invasion and occupation of this region had been completely unopposed by the Americans on their own home turf (which is utterly unimaginable), the logistical requirements to support a Japanese occupation army across 6,000 miles of ocean – a trip of about one month by fast ocean liner – would have been impossible to meet. The Anglo-Americans had a tough enough time supporting their own forces in Normany and (later) in western Europe in the weeks and months after D-Day, even though all that separated Britain from Normandy was the English Channel. And the Japanese themselves found it very difficult (and ultimately impossible in the long term) to supply their relatively close troops on Guadalcanal, despite the best efforts of the Tokyo Express.