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I saw a training film once that showed how the Japanese were able to move through rough terrain quickly. It was like watching ants cover uneven ground by employing carried mini bridges. As I recall, the Japanese were also masters of camouflage at that time. Setting up in the mountains in covered and consealed positions would give them the advantage over troops coming across the plains and having to attack up hill. Americans didn't really use camouflage for the most part at that time as I understand.
It is hard to believe that Japan had 6M tons of shipping to devote to one campaign in 1939. Are you sure of those figures? As far as distances all of Torch was not supplied from the US but also from the UK as well. Any invasion of the US west coast by Japan would have to be ready to deal with the likelihood of British and Commonwealth naval forces becoming involved also. Would a Japanese invasion force leave Hawaii in their rear? By the way the distance from Tokyo to Los Angeles is more than 5400 miles. In 1939, does Japan have the suitable tankers to keep a naval force fueled for that difference.
Further research shows that in 1941 the Japanese merchant marine comprised 6M tons of shipping total. Of that 3M tons was needed for the home islands. I doubt they had 6M tons in 1939. How do they get 6M tons for an invasion?
Thank you Shinpachi san, much of this I didn't know. Some I've heard but not in any depth. Ok, so the first moves of Japan were defensive in wake of Western powers looking for colonies and empire expansion. That makes perfect sense. Do I understand this correctly Shinpachi san? So the first steps then to prevent later war could have been the introduction of business in China rather than conquering it and making it a colony. Nation building to further business interests. What do you think Shinpachi san?
All infantrymen of WW2 could move quickly over rough terrain. Nothing special about the IJA about that.
But terrain dictates logistics. And the rougher the terrain, the more difficult it is to keep the troops supplied.
The topography of the US western states is so rough in every location, and is several hundred miles "deep", that the Japanese would need months if not years of engineering work and supply buildup to strike eastwads across multiple mountain and desert ranges, through many types of weather.
The only thing the Japanese could do is land their troops and watch them go no further than the coastal areas. And all the while, the US manpower and industrial engine revs up.
Your understanding is correct and no nation should not rely on their military power when they do business.
Japan was wrong on this point.
4)
Saying the Rockies are an impenetrable barrier is akin to the french saying the Ardennes are impassable. Given the ability of the Japanese to overcome far worse terrain to defeat their enemies clearly demonstrates that the japanese would have had sufficient infrastructure in the form of the rail network and the local road network to undertake their crossing of the mountain regions you are now pinning you hopes on.
The Japanese never had the amphibious and logistical assets to ever invade Hawaii, let alone the mainland US. The concept of them having this hypothetical capability is more in the realms of fantasy than "what if".
The best they could do is station a bunch of subs near the main ports and then get results as good as, or even better than what the Germans got with Operation Drumbeat.
The main Japanese thrust must always be into SE Asia, followed by advances into the shipping lanes going to Australia. The Japanese desperately needed the oil resources of SE Asia before they committed any forces to a wild goose chase in Hawaii, let alone the mainland US.