Friar Bijou wrote:
That's kinda the (whole) point of this OP. Rather than a "strike" this could easily have been a full blown invasion of the islands if they had thought it through.
Try not to back-view what did happen and follow through on what could have been. Again....what they were capable of and failed to do.
Ok. Here's what likely would have happened. First possibility: Japanese forces delay the air attack to coordinate with the invasion force:
Once the Japanese fleet got within a couple hundred miles of Hawaii, they would have been spotted. At that point, the islands would have gone on high alert. All the personnel would have gone to their defensive positions. Anti-aircraft guns would have been manned, aircraft would have been launched, fast moving ships would have been deployed in a picket. By the time the Japanese could have attacked they would have met stiff resistance instead of total surprise. The larger fleet ships would still have been in harbor (takes quite some time to get them up and moving), but would not have been nearly as defenseless. The low flying torpedo ships would not have been nearly as effective, and the higher flying dive bombers would have had to get through a large amount of defensive air power. In all likelihood, the attack would have been a failure, ground forces would have barely been able to land much less been able to effectively capture any ground. It would have had all the negatives of an attack on the US, but with none of the positives of actually hurting our military. And the cost would have been massive for the Japanese.
Second possibility: Japan makes the same surprise attack it did historically, but then follows it up a half day or so later with an amphibious assault on the islands.
This is presumably what you're thinking of. They just bring some troops transports and then take advantage of the chaos and destruction their surprise strike caused to land troops and take the islands. This is good in theory, but is problematic. Remember that they launched from several hundred miles away in order to avoid detection. This was sufficient for waves of attacks, but they were pretty much at the end of their effective safe attacking range (ie: they could not loiter around the battle, but had to strike and then return). But it would take the better part of a day for the fleet elements needed to land a ground assault to arrive at the islands. Yamamoto actually called off a planned third wave because air defenses in Hawaii were starting to respond and the cost/benefit of another wave wasn't worth it (fewer high value targets and more likelihood of losses to their own forces). The air attacks did not focus on island defenses, but on the fleet and air bases. It didn't need to because they counted on surprise to avoid having to deal with those defenses. Had they attempted to cover both, they'd have done less damage to the naval infrastructure, possibly very little. Remember, this was all about resources expended compared to costs to the enemy. They could have gone all in, but it also very likely would have ended in disaster. Hawaii did have a significant number of military personnel. By the time a full invasion could have occurred in this scenario, those forces would have been fully prepared. Even just a whole bunch of armed guys manning artillery and anti-aircraft weapons would have been sufficient to make any assault incredibly expensive.
I just don't think that they *could* have sent sufficient forces and been able to successfully take the islands. And, as I pointed out earlier, even if they had, they did not have the resources to maintain Hawaii as a military base. The US would have still rebuilt its fleet and the first place they'd have retaken would have been Hawaii. The idea that Japan would have maintained a fleet presence in Hawaii is interesting, and it's possible they could have made life very "interesting" for the US west coast, but it really does come down to the sheer distance. Hawaii was just too far for Japan to maintain with the capabilities of that day.
Japan was much better off doing what they tried to do. Had they been able to consolidate the South Pacific completely (specifically taking even portions of Australia), they could have similarly prevented the US from being able to do anything. The distance issue applies in reverse as well. The fact that Japan was not able to consolidate in the South Pacific shows that they certainly could not have done so in Hawaii. The same problems would have existed for them (failure to prevent us from supplying and using Australia and other islands as bases), but would have been much worse since they'd have had to keep significant resources in such a precarious position in Hawaii.
If Japan had possessed significantly greater resources, they could (and perhaps should) have taken and held Hawaii. But then again, if they'd possessed those resources, they wouldn't have needed to attack in the first place. Their entire reason for war was to gain access to greater resources they felt were needed to create an empire. The attack on Hawaii was intended to buy them the time to do so without US interference, and frankly it worked about as well as one could have hoped. Since that still wasn't enough to prevent defeat, it's hard to imagine any other scenario they could have tried which would have altered the ultimate outcome.