castor brings up some excellent points, and since my game vs. Canoe was cited, I'll weigh in.
I don't get the panic here, either. I am very interested to see what PH makes of this Northern Expedition, but my first reaction was that it's a big investment in a sideshow. Actually invading the West Coast would be doing you a favor, with all the Restricted units you can use, plus the 6 divisions or so you get extra as unrestricted reinforcements. He can bomb Seattle, which is the main concern; but I think he needs Victoria to do that effectively, and I think landing on that row triggers the big reinforcement. Conducting a major bombing operation from Coal Harbor isn't easy; he can use sweeps over Seattle to really knock down alot of your fighters, but you have tons of fields to run B-17s from, with ample AV support, to keep Coal Harbor in check.
He will have to keep an air presence, CVs or otherwise, in the Gulf of Alaska to prevent you from raiding his supply lines with DDs and whatnot. The supply line to Coal Harbor is pretty narrow.
Once Seattle is secure, and you are confident he isn't launching an air campaign, I wouldn't bother with a major effort to re-take Alaska. Why do you need it? Other than to threaten the Kurlies, you don't. And, as you get closer to 1944, it will become a huge trap for Japan. At that point, you could just land in the Aleutians, and isolate whatever is left in Alaska. If he has evacuated, retaking it will be easy.
The main impact is that I do see it diverting a good chunk of your air strength, and retarding your training program a bit, as the Restricted Air units that are normally just training are on extra duty. Even here, though, alot of the air strength you are committing will be units that are stuck on the West coast anyway, including P-38s.
I also agree with castor on Hawaii: Against a good opponent, there is no chance. Pearl Harbor starts with a pile of Engineers, 2 Infantry Divisions, and enough CD guns to make any landing expensive. The only viable airbase to control the Hawaiin skies is Lahaina; everything else requires too much time to build.
Australia is also impossible vs. a good opponent. Moving the San Diego Marines there is a good idea early, as well as some Marine air and extra units, especially fighters. But it shouldn't take a ton. The Aussie Militia units are OK, if they are set to digging right away. In this game in particular, the IJN is needed to cover the Gulf of Alaska; he can't do that, AND cover Australia.
India is much more vulnerable. The Indian Army starts out in terrible shape, and the RAF is very weak early, with inadequate replacements for everything. It's also a very short hop from Singapore, and doesn't require much Naval commitment once you are ashore (unlike Australia, which will require CONSTANT IJN commitment).
If he makes another move, I think it will be India, because you can pull that off as Japan without a big naval commitment. I don't think the IJN can cover both North Pacific, AND Australia; too much sea to cover, too far apart.
Actually the Aleutian chain was very easy for me to take back in a winter campaign in 1943. Using LSTs the Allies can just leapfrog to un-held or lightly held zero port bases of which there are a lot. These can be built up and used to support the next leap and to cut off major Japanese bases. As soon as spring weather hit, I invaded the few major Japanese strongholds and it was over. I should not have been able to do it but it was remarkably easy. Winter weather really did not hinder my air ops much.
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