Deleted member 1487
I don't disagree that the Japanese were very weak given a potential Soviet invasion. The question is how much the Soviets could project across the border into Manchuria where the rail gauge was probably different (don't know for sure) with a similar 5:1 advantage at Khalkin Gol to get similar results and push the Kwangtung army back into Korea. I highly doubt the 1939 Soviet military writ large was anywhere near as capable as the Khalkhin Gol forces. They were able to project a couple hundred miles, but Manchuria is much larger than that. The Soviets just didn't have the logistics to push the Japanese out of Manchuria and I strongly question how much their tank and aircraft force in the Far East was operational. They might be able to project a fraction of their overall strength across the border, which wouldn't be enough to budge the Kwangtung army. Now the Soviets were formidable on the defense when they weren't having to project on foreign soil, but their 1939 major war record was not stellar in Poland or Finland. Any conflict in Manchuria was drag out, be very bloody, and compromise Soviet security in Europe badly. That's not to mention what happens with Poland, Finland, and the occupation of the Baltics/Romania in 1940.There is some substance to this argument: the 23rd Division at Nomonhan was by far the greenest outfit in the Kwantung Army. It was widely derided and had hand-me down equipment. The Soviets meanwhile demonstrated that owing to their nominally defensive stance in the Far East they needed a considerable period of time to gather the resources necessary to push a beefed-up corps a relatively short distance across an open plain, not like the thousands of empty kilometers of the Manchurian heartland.
The problem is, as of February 1939 (a couple of months before Nomonhan) the entire Japanese Army in Manchuria numbered 359,000 people, 1,052 field guns, 585 tanks, and 355 aircraft. Korea contributed another 60,000 men, 264 field guns, 34 tanks, and 90 aircraft to this total. Against them the Soviets had thousands of tanks and planes, with probably twice the number of men. Although any offensive would obviously proceed relatively slowly the force ratio at this time is not in favor of Japan. Still, reconsidering this I partially retract my above statement: the Japanese probably could have held onto the industrialized areas in central and southern Manchuria with the forces on hand, but still given the USSR's warmaking potential and the fact that Japan hadn't yet fully mobilized Stalin could probably still strong-arm some concessions out of them the way he later did with Finland.
I'd agree that Soviet productive potential is quite high, but at the same time how much could be projected along the Trans-Siberian RR over 6000 miles? Vladivostok would be blockaded by the IJN. The US would probably give Japan a lot of leeway given that they weren't all that happy with the USSR either. Japan would go to fully mobilization and though they'd prefer to not have to fight a two front war, would probably due to 'honor' have to fight it out and reclaim their pre-war borders.
In fact a major war with Japan in 1939 and on is probably the best thing Germany could possibly hope for for 1941.