I think it is a reasonable assumption that the Japanese would be VERY cautious about any moves towards Russian Alaska... having taken great strides to disengage themselves from the War with the USA (and ever more powerful USN) it would be foolhardy to move on Russian Alaska as that would clearly be seen as a challenge to the USA's now hegemonic influence in North America. Why needlessly antagonize the newly nuclear USA when there are so many other easy pickings in the Asian pacific rim? Logistically the Aleutians are also cut off by thousands of miles of some of the harshest winter oceans in the world from Japan's main holdings in Asia. I think its safe to say that while the IJN may have a wish list that includes Russian Alaska there is very little chance (no way) Japanese imperial leadership would jeopardize reigniting war with the brand new USA superpower.
Just my $0.2
Thank you for that, I greatly appreciate it! I apologize in advance for what might be impassioned statements. I got a lot to say on this subject, as you'll see soon, so I apologize.
By the "end" of the war in the summer 1944 in TL-191, the assumption that the United States has "hegemonic" influence in North America is still fairly tenuous to me. Canada, while fairly subdued, is still under military occupation and still hosts rebel cells willing to fight against the United States, something that Japan as exploited in the past during 1920s and 1930s. Though those efforts failed, these rebels are by no means gone and unsupported. And then there's the former CSA to consider and Utah to a lesser extent, with even more fervently defiant populations still unwilling to call themselves Yankees. Military occupation and martial law will have to be an unfortunate necessity to keeping the southern states under control. That will require many men and resources that the United States will definitely need to keep the lid down on things. Consolidation, reconstruction, and enforcement of a new authority over the southern states would be the United State's priority despite a willingness to police world affairs when it comes to atomic weaponry.
It is
also a reasonable decision that striking the Aleutian Islands is, in my opinion, as cautious as the Japanese can get
if they decided to send forces there. Siberia would be the main theater of operations for their probable offensive into the Russian Far East in 1944, no question about it. It would require many men and resources and the region they wish to control in Siberia holds much for them to take. Alaska
as it is in TL-191 holds no value to the Japanese - this assumption I agree with and I actually don't believe they have ambitions to even try to take Alaska away from the Russians.
The importance of the Aleutians, in my opinion, and
strictly the Aleutians, is another story. Their value is in where they lie in the sea and what the Japanese can do to put more strain on the Russians to get them to the negotiating table on less favorable terms.
They would deny the Bering Sea and possibly the Bering Strait to the Russians, cutting off Alaska and cutting off another source of possible reinforcements for the Russians to send west into Siberia via sea lanes. To secure a possible flank from which the Russians can transport troops into Siberia. From these islands, if they manage to build airfields on them, or take islands with existing airfields, they can also potentially strike at naval bases in Kamchatka where parts of the Russian Pacific Fleet could be anchored, especially at Petropavlovsk-Kamchatsky. I believe that any serious move into Siberia would also put the Russian Pacific Fleet (if there is one in TL-191) on a high alert status - Vladivostok would be a primary target for the Japanese and the Russian Pacific Fleet's headquarters would be there. If the Russian Pacific Fleet moves in response to an invasion of Siberia, the Imperial Japanese Fleet will have to respond.
Now, taking that into account, it
would be foolhardy of the Japanese to attack the Russian Alaskan
mainland in North America itself. It would be out of their operational limit. With troops setting foot here I believe this would set off more of an alarm to the United States and would be cause for serious worry. This is something the Japanese would not want to have and would be an unadvised move. But to be fair Alaska is still Russian territory. Not United States territory. This is something the US will have to consider too.
Even if the US was to respond to movements in the Bering Sea, what could they respond with in time? Would they
really get involved in a possible war between two former and feuding Entente Powers? The same logic of traveling thousands of miles to the Aleutians, to some of the harshest winter conditions in the world, also applies to United States. Without a Panama Canal in place that travel time is doubled for the existing fleet in the Atlantic, with any force concentration bound to be noticed by the Japanese. The US Navy in the Pacific in TL-191 by 1944, from what we are aware of, only has two escort carriers in the Pacific, with their only fleet carrier sunk and with the only other known carrier possibly in the Atlantic. The Japanese Navy most certainly have their own escort and fleet carriers prowling the Pacific and they certainly have more of them to spare. The US Navy in the Pacific would be dealing with a Japanese Fleet that is much more potent and much more well supplied, given that the Japanese had control of the oil of Dutch East Indies since the inter-war years in TL-191. It would be tough going for the USA even with the Sandwich Islands in their control. The Japanese have demonstrated in the past that they have the capability to strike the US west coast as well, with far more potency than they did in our timeline. They have done so multiple times with varying degrees of success. Regardless, it is a capability that the US is aware of and should greatly consider before going off and teaching Japan a lesson.
With regards to the USA being a nuclear superpower that Japan should not mess around with - again I believe that's debatable. We can't forget that Great Britain has also demonstrated that it has created the atomic bomb in this timeline - and Japan attacked them regardless, specifically they attacked British colonies in Asia and the Pacific. Britain has also demonstrated the capability to use it as well, having dropped a bomb on Hamburg, Germany, with another bomb ready for use before the bomber carrying it was shot down. By June or July of 1944, the Japanese are very aware that Great Britain has the capability of producing atomic weaponry and delivering it. By this time it is also aware that the United States and Germany have the bomb. And yet by the end of the Second Great War Japan is the only great power to emerge from it still intact and without getting nuked - and its still growing. Even if the US was to make another atomic bomb and put it on a bomber to try and intimidate Japan, the distance to deliver that bomb is a long way off from striking anything important within the Japanese Empire, even if it was coming from the Sandwich Islands or Midway or Wake. If bombers can't hit the home islands or its major colonies, then the US doesn't have the intimidation factor. It too would be needlessly antagonizing Japan. Simply put, the US doesn't have the force necessary to intimidate Japan into complying with their wishes in the summer 1944. Later, yes, but as things are in 1944 TL-191, I don't think so.
The Asian holdings on the Pacific Rim are either in Japanese control, are about to fall under their control, or are being contested by the British, the only power in the Pacific with a navy capable of defying the Japanese, even during the late stages in the war, although it is battered and stretched across the world. The Philippines, Indochina, The (former Dutch) East Indies, the port cities along China's coast and multiple islands across the Pacific are already under Japanese control by the end of the war and the US Navy has failed to contest those territories. Soon or presumably soon Malaya, Hong Kong, and Singapore will fall to the Japanese. Its run out of Pacific islands worth conquering really, besides possibly the Sandwich Islands, Midway, and Wake, the later two they merely just abandoned after taking them from the US.
I'm not denying the US is a nuclear armed super-power in TL-191. It certainly deserves that title. But its a country that has been deeply scarred and battered because of this war, fighting the Confederates in a massive battle to the death, one in which nuclear bombs were dropped on its own soil. It has shown the willingness to face down countries it sees as a threat and the US government has shown a desire to check Japan's ambitions in the Pacific. Japan is a world power, arguably a super power in its own right in TL-191, a true equal to the United States in terms of military power and force projection. The Pacific is divided in influence and Japan arguably has an advantage. The US will be able to properly contest Japan in TL-191 in due time believe, its inevitable. But in 1944, just after a massive war, to imply that Japan should not mess with the USA because it is now in possession of an atomic bomb is debatable... especially given that Japan may be looking to develop one of its own in TL-191.
If the United States wants to get involved in a possible war between Japan and Russia over possession of Siberia due to both countries potentially squaring off up north in the Bering Sea on the Aleutians, then I believe the United States seriously needs to consider the options it has before going in and trying to intimidate Japan out of the area.