You haven't heard of the Burma Road then? IOTL, in the dire early stages of the 2nd Sino-Japanese War, it only took a year to construct, with the project commencing in 1937 and completed by 1938; and the construction of the first and by far the most difficult section of the Ledo Road extension into India, across the Patkai range, took roughly the same time. It'd certainly take the KMT Chinese longer to construct these supply routes in wartime conditions, but it'd be just a matter of time- and if the Burma Road is still constructed ITTL, the initial supply route is already in place from the outset of hostilities in the South Asian Theatre of WW2.
I'm familiar with it, yes. Thanks for the sarcasm. All right, then, let's imagine that China builds the Burma Road. I will assume that the Second Sino-Japanese War never happened ITTL, because planning to invade Burma either during or right after a devastating war is insane. So, why is the UK allowing a presumably unfriendly, German-aligned China to build a road to one of their colonies? Even if they allow it, I imagine they will prepare to defend themselves against troops that do come down it. The British had a very specific reason to build the OTL road. It is not like you can build a new road between Burma and Kunming in peacetime at extraordinary expense and not raise eyebrows. But I'll give you the benefit of the doubt. Let's say the Brits are distracted, and they buy the idea that the road is just to promote trade between Burma and Kunming. A Chinese army starts walking down the road. How do the Chinese keep the British from closing the road? The OTL Burma Road worked specifically because it was so far from the fighting. How will the Chinese keep it open when it is on the front lines, when the British have air support and they just don't? Finally, the reason the Burma Road was useful in OTL was because it served as a transport link for trucks carrying tons of supplies. But China doesn't have trucks. They can't build them themselves, certainly. I suppose they could import some, and the oil, and the spare parts, but it won't be easy to keep more a relative handful going. As you keep saying, the advantage of China is their large population. If they send (march) in these huge armies into Burma, how will they keep such large numbers supplied with the British interdicting their sole supply route, which they don't have the trucks to really make useful anyway?
Another reason why a military alliance with a more successful KMT China would be considered a viable alternative to an alliance with the Japanese. For him the number one enemy would always be the Soviet Union, not the British, French or U.S of Americans; and when taking on the Soviets, what use will Japan's shiny modern navy be to the Nazis in the conflict? An ally with a vast reserves of manpower which can be thrown into the conflict, outnumbering even the hordes of troops which Soviet Russia can mobilise with ease, would seem to be far more useful to Nazi Germany.
As I have said more than once, the issue is that China is not a threat to the Soviet Union at this time in any way, shape, or form. China's population is much larger than Japan's, true, so in theory they can field larger armies. But again, how can you keep them supplied? As you can see from what I wrote above, I have serious doubts about the potential of an alt-Burma Road to do so, but in fighting the Soviets you wouldn't even have that. China had significant trouble in this time period keeping their troops supplied with rifles, bullets, and food
in China. How do you propose to do so in the wastes of Siberia? Finally, even if Chinese armies would be far larger than Japan's, they will also be far less effective. It is well-known that Japanese armies fared badly against their Soviet peers at Nomonhan. But at least the Japanese had a fighter (the Ki-27) which could go head-to-head with the I-15 and I-16. At least the Japanese had bombers to hit Soviet airbases. Japanese 37mm anti-tank guns were fairly ineffective against Soviet armor, and they didn't have enough of them, but at least they existed. China can field a big army, at least in theory, but sending a half-starved short of ammo Chinese army to fight against the Soviets with no air cover, no anti-tank weapons, no tanks, and very very little artillery is not going to be an effective strategy.
The Chinese knew this as well as the Germans did.
IOTL, the Japanese had the momentum and the firepower to continue their advance far further into India after the Allied retreated from Burma in disarray in May 1942, but refrained from renewing their offensives after the monsoon. The reason for this seems obvious enough- the size of the Japanese force deployed in the Burma campaign just wasn't large enough to simultaneously continue the advance into India and occupy their newly conquered territories across South-East Asia. ITTL, the Chinese would have more than enough troops at their disposal for this to be a non-issue, at least until they manage to push as far west as Bengal.
The fact that they were running low on manpower was crucial, but so was the fact that they were reaching the end of their supply tether. And their supply tether is infinitely longer than any a Chinese army would have. Once again, having a lot of bodies to put into the army doesn't matter that much if you can't keep them in ammo and food.
The key to either a Chinese or Japanese ally would be to upgrade their armor to be able to more effectively oppose Soviet armor and artillery. My understanding is that the Japanese army opposed the Soviets once or twice during the Japanese invasion of China (The China Incident). The result is that the Soviets are more effective use of armor and artillery which shocked the Japanese.
The Japanese Army would need to upgrade their armor starting around '36 or so to be able to effectively engage Soviet forces.
I have my doubts. Militarist Japan was able in OTL to build fighter designs that were competitive (or would have been competitive, if not for shortages of good-quality alloys, fuel, spare parts, etc. near the end of the war) with almost anything the Allies build during the war. It didn't matter, though, because they could never build more than a relative handful of them. If Japan receives detailed blueprints of advanced tank designs early in the conflict, that could help immensely, but I still don't think the state of the Japanese motor, steel, etc. industry would allow for more than a relative handful to be build. I don't think it would ever really be enough to go toe-to-toe with the Soviets.
I'd almost say ASB, or butterflies from about 1300 A.D.
Japan considered Korea's only purpose being a staging ground for the invasion of Japan. And of course, once a Japanese invasion of Korea is under-way the Chinese are looking at Korea's only purpose being an invasion staging ground by Japan.
Difficult to see how this would be dealt with.
1300 AD? Seriously? I mean, one could argue that the Teutons have been expanding at the expense of the eastern Slavic peoples since the middle ages, but no one uses that as a reason why Operation Barbarossa was inevitable. A Japan that begins to expand abroad will inevitably expand towards China, as it is an obvious target. However, let's not forget that, for example, in 1928 Japan was pushing
for Chinese tariff autonomy (under a liberal internationalist foreign minister), much to the delight of the KMT and the disgust of the other concession holders (the US, the UK, France, etc.) It is easy to think of PoDs that would prevent the Second Sino-Japanese War if you go back about a decade before it started. If you allow yourself to go back two decades, it is easy. Certainly a PoD going back to the 1300s is far from necessary.
