Interestingly enough, Prof. Theodore F. Cook (known mostly for his book "Japan at War: an Oral History") wrote an Alternate History scenario in which the Japanese pulled a "reverse Midway," sinking 3 American carriers in exchange for 1 of their own, followed up by a successful F-S and invasion of Hawai'i. The article is below:
Hawai'i Invasion: Leis for the Emperor
Theodore F. Cook, Jr.
Almost from the outset of war, planning for an invasion of Hawai'i stirred controversy at the highest level of Japanese military leadership. On January 14, 1942, Rear Admiral Ugaki Matome, chief of staff of the Combined Fleet and Yamamoto's right-hand man, confided in his diary that Japan had to make the attempt "to take Midway, Johnston, and Palmyra after June, send our air strength to those islands, and after these steps are completed, mobilize all available strength of invade Hawai'i, while attempting to destroy the enemy fleet in a decisive battle." He knew many would likely oppose his plan, but among the reasons he listed for why it had to be executed were: "What would hurt the United States most is the loss of the fleet and of Hawai'i"; "An attempted invasion of Hawai'i and a decisive battle near there may seem a reckless plan, but its chance of success is not small"; "As time passes, we lose the benefits of the war results so far gained. Moreover, the enemy would increase his strength, while we would have to be just waiting for him to come"; and "The destruction of the US fleet would also mean that of the British fleet. So we would be able to do anything we like. Thus, it will be the shortest way to conclude the war." Ugaki noted too that "Time is an important element in war. The period of war should be short. Though a prolonged war is taken for granted, nobody is so foolish as to wish for it himself." Each of these reasons would still have seemed valid after a Japanese Midway.
That Hawai'i was the next target for the Imperial Navy after the seizure of Midway is nearly certain. Thanks to the prodigious efforts of John Stephan of the University of Hawai'i presented in his book, Hawaii under the Rising Sun: Japan's Plans for Conquest After Pearl Harbor, we have a pretty good idea of what Japanese thinking was in 1941 and 1942 for a Hawai'i operation and invasion. The Japanese faced formidable obstacles to success. Certainly a Japanese jump to Pearl Harbor would have been a tremendous gamble, but it would have become a much better wager with the US carriers sent to the bottom and the Hawaiian Islands partially isolated by free-ranging Japanese carriers and submarine forces to their east. Having come this far, Yamamoto surely would have made the attempt if he could pry out of the Imperial Army the divisions, aircraft, and supplies needed. Despite the risks, the potential benefits to Japan of a successful seizure of Oahu are hard to exaggerate, so much so that one can even argue that the only way Japan could have hoped to stave off defeat long enough for negotiations may have been with an all-out assault on the islands at the onset of war. But that is another path off our chosen counterfactual road.
Eastern Operation's invasion of Hawai'i was planned to unfold over a period of months, in a series of stages, though had the victory at Midway been as complete as suggested in this scenario, calls would have been raised to speed up the timetable. To strike immediately would take advantage of American confusion (not to suggest panic) but it would also invite complete disaster. Oahu, the island where Pearl Harbor was located, could not be taken by storm; its fortifications, garrison, and air bases were formidable and would have to be reduced before any invasion could be attempted. The Japanese sword needed to be kept sharp through time in port and under refit and the carriers' aircraft and aircrews had to be rested and replaced. Yamamoto could not have continued to keep his fleet at sea, flitting from one "triumphant operation" to the next in preparation for a culminating battle for Hawai'i, even were he able to find the fuel to do so. Moreover, the Japanese navy would have to secure the full commitment from the army to supply the men and planes needed for the job-not just the few designated before Midway. This would be no small task as they had opposed each of Yamamoto's offensives to this point in the war. But a great Midway victory might have made them enthusiastic supporters, though it seems that few in Japan shared Yamamoto's view that the Americans would be willing to negotiate after Hawai'i was in Japanese hands.
With a clear objective, timetable, and the attention of the commander in chief of the Combined Fleet, Yamamoto Isoroku, the plan most likely to have been attempted posited a strangling of Hawai'i from the west and southwest by a careful move against Palmyra Island as the key air link leading on to the South Pacific, a completion of operations in the FS Operation by taking Samoa, and the establishment of Japanese air and sea bases in September. This the full-blown invasion of Hawai'i might be executed in late 1942, perhaps December. This plan had the advantage of allowing several more carriers to join the fleet and provided for a rapidly accelerated program of converting seaplane tenders into aircraft carriers. Preparations for the Hawai'i Campaign were grandiose, but might have been just feasible if America's military forces were crippled at Midway. Like a great scythe sweeping across the southwest and south-central Pacific, the first phases of the operation, following the theme of the original FS (Fiji-Samoa) proposed before the Midway invasion would sever the lines of communication and supply that tied Australia to Hawai'i and the West Coast of the United States. New Caledonia, Fiji, then Samoa were to be seized (perhaps even Tahiti beyond). Each leap supporting the next. This would be accompanied by landings on Johnston Island and Palmyra Island, another featureless point in the Pacific, leaving the Hawaiian Islands as the only US territory left in the Central Pacific.
American defenses in the Hawaiian Island chain had grown stronger since December 1941, when US Army troops had numbered 40,000 and probably exceeded 65,000 in April 1942. Even larger garrisons were projected for Oahu, home of Honolulu and Pearl Harbor, and for Hawai'i, the "Big Island," several hundred miles to the southeast. But these reinforcements would have posed immense problems for American commanders in the coming battle. Hawai'i was not the rich island paradise of the travel brochures and prewar navy recruiting posters; provisioning the troops and feeding the civilian population, especially the large concentration of people in Honolulu, would have been a nearly impossible task without easy access to maritime supply. Poor and underdeveloped, except for its pineapple and sugar plantations, the Hawaiian Islands were heavily dependent on imported food, and virtually all the supplies necessary to support the civilian economy, to say nothing of the massive needs of the military forces, had to be imported. Most supplies came from US ports more than 2,000 miles across the Pacific to the northeast. Estimates of Hawai'i's food supply on the eve of war were on the order of weeks, rather than months.
The utility of Pearl Harbor and the other facilities depended on the local labor force. Moreover, 160,000 of the residents, more than 40 percent of the population, were what the Japanese at the time called doho, meaning "compatriots" (a term embracing ethnic Japanese at home and abroad, regardless of their citizenship.) It must be said that prewar US Army planning for the defense of the islands rated the loyalty of second-generation Japanese (known as nisei) quite high; the Hawaiian Department even recommended recruiting nisei soldiers. Despite the Draconian practices employed on the West Coast, very few Japanese Americans or Japanese nationals attracted the attention of US security authorities-less than 1 percent of Hawai'i's population of Japanese descent were interned. Nevertheless, Japanese planners were hoping for a mass rising of "fellow countrymen" when Imperial forces arrived and planned to make good use of a sizable number of Japanese with Hawaiian experience identified in Japan once the islands were conquered for the Emperor.
What means had America to contest operations against Hawai'i, to supply an expeditionary force there, or to sustain any large-scale operation from the West Coast? Air operations were impossible from the United States against Hawai'i-no bomber or transport plane could fly there fully loaded until the B-29 in mid-1944. As we have seen, an overwhelming Japanese victory at Midway would have left no American carriers to contest a Japanese invasion and taking back Hawai'i, should it fall to Japan, would have required a massive seaborne operation, on a scale the United States could only mount in late 1943. What a prolonged Hawaiian campaign might win for Japan must be assessed against what the diversion of force and effort of a greatly outnumbered fleet would have cost the United States. Without a fleet-in-being operating out of "America's Gibraltar," Pearl Harbor, Hawai'i Territory's capital, Honolulu, and the island of Oahu were not protected from attack. Its principle defense, besides the coastal guns protecting the harbor, were the planes on Oahu's airfields. Even in the age of air power and the capability of aircraft to strike far out to sea and patrol, keeping the planes aloft depended on supply by sea.
The most likely scenario for the final Japanese assault on the Hawaiian Islands would begin with a strong diversion aimed at Oahu and a carrier-covered landing on Hawai'i Island in an effort to secure forward base facilities at Hilo; rapid construction of airfields to support the bombardment of US Army and Navy installations on Oahu would follow, as the Imperial Navy brought its bombers and fighters from the south. A furious series of air battles would be fought, and while the Americans could be expected to do well and the Japanese planes and pilots operating at the end of a painfully thin line of supply, the Americans, without a fleet-in-being to truly threaten the Japanese, would likely not be able to sustain the struggle indefinitely. Spare parts, ammunition, replacement pilots, to say nothing of fuel and new planes, would have to run the gauntlet from the United States and would be most vulnerable as they approached the islands where cargo ships could be intercepted by units of Japan's fleet. If no "rising" had occurred among the Japanese American population, it seems likely that civilian targets on Oahu would be subjected to merciless air attacks and the US fighter force gradually whittled down. There is no doubt that a direct assault on the harbor at Pearl would have been suicidal, and it is likely that the American garrison would have made the northern beaches of Oahu- the most favorable landing sites-quite impregnable to direct assault. But it is possible that elite units of the Imperial Army, such as those used in airborne assaults in Indonesia, could have been employed after the American defenses were hammered by the battleships of Japan once the US air defenses had been suppressed or exhausted. Japan's attacks across the beaches would take terrible casualties in their assaults, but with sufficient fire support from the fleet, they might overwhelm the defenders and force the ignominious surrender of yet another American Pacific bastion.
Nowhere in the Imperial archives can we find a plan to extend the Imperial sweep further eastward, but, while Japanese fleets or squadrons probably could not operate effectively far beyond Hawai'i, occasional raids in force, or lucky cruiser strikes against a few high visibility transports bound for Hawai'i in desperate US efforts to reinforce the islands, could have been very bad for American morale. Also, Japanese submarine raids against the West Coast 2,000-odd miles to the northeast-like the shelling of isolated outposts-surely would have heightened tension there and perhaps even have been of some military utility. Hunting packs of Japanese subs, with supply subs as mother ships, or resupply vessels, might have threatened coastal traffic until long-range patrols were established, as they were in the Atlantic. Deploying a few submarines off Panama could disrupt shipping in a major way, even if they could not stay on station long, while a bold raid on the Panama Canal, employing aircraft carried by Japan's largest submersibles, flown on a one-way mission from close in, loaded with high explosives, could have wreaked havoc were they able to seriously damage even one of the locks; again the threat would likely have tied up even more American forces.
