Heres some info i found for Japanese ground forces.
Japanese strengths were in firepower and mobility. They did not do well with combinded arms tactics and had an outdated force structure.
Japanese relied heavily on artillery. In Manchuria they had 5360 artillerty pieces, in China over ten thousand. They "almost always had artillery superiority on the battlefield and were well trained in fire support coordination. The Artillery calibers tended to be light,77mm or 90mm guns were common, but battalions of 150mm howitzers were also avalible to reinforce attacking divisions. Japanese infantry battalions also had organic platoons of infantry guns or light mortors for direct fire support. Firepower was mobile and 'up front' where it was needed."
Japanese "had, on a whole, greater tactical and strategic mobility" than most of their advasaries. They were masters at infiltration, the use of light infantry and ambushes. They were able to stand up to the most mobile units the British had avalible the Chindits under the command of Orde Wingate. They were able to inflict heavy casulties on these elite British units in 1942-43. The Japanese in one incident were able to annhilate two whole companies of these units after springing an ambush and letting lose acurrate mortor and rifle fire.
The Japanese overall force structure and orgainzing was disappointing. Their reserve system was based on the Prussian 1870's pattern and their overall organization of their divisons was based on the outdated 'Square' pattern of WW1. It was only late in the war that they modified their force structure to a 'Triangle' pattern.
Brian Train is fairly inaccurate in his appraisal.
The Chinese simply didn't have much artillery at all.....hence the Japanese always had artillery supremacy. It's the same fact with Armoured Cars and Tanks in China. The Japanese Army in China had such equipment, but the Chinese didn't.
Where the Chinese did have 'modern gear' it was often in the early war phase deployed piece meal, then later Chiang was more loathe to deploy it because the Nationalist Army had lost quite a bit of what it had had, earlier in the war.
Hence the Chinese Nationalist forces never really deployed much equipment.
Indeed, Japanese equipment superiority over the Chinese was such that they only needed to fire off a few rounds at a dug in Chinese position to dislodge the Chinese, since the Chinese were never really able to fire back. This led to the Japanese spreading out their armoured vehicles and guns among the lower officers.
In essence, the Japanese come to the infantry support doctrine, more by the fact that the Chinese don't have any real counters, than from any military 'theory'.
Artillery was always considered a 'direct branch of the infantry' in Imperial Japan as so had its command and control structure was geared around that. The Japanese very very rarely co-ordinated battery fire, and so by all standards, the Japanese hardly used their 'suppiour fire-power' to it's 'fire power effect'. This would hurt them later in Burma and during the early pacific campaign in OTL when artillery was not employed 'en masse' against Allied Offensives. If it had been, then some of the very costly later island battles like Iwo Jima might have been brought forward when the Japanese realised that the most vulnerable point of an invasion was just as the first waves of infantry had landed on the shore.
But anyway I digress.
The Japanese never had 'a strength in fire-power', they only had a relative superiority vs the Chinese who had even less.
In terms of mobility, he/you are spot on. The Japanese Armed forces lacked motor transport, not only because of engineering, but simply because the fact was the roads were not up to Japanese Motor-engineering of the day.
However, because of that the army knew that their guns would be either manhauled, or hauled by horse/mule. Hence the guns were designed with that very aspect in mind. Indeed, one gun one of the 74mm ones could be broken down into pieces and carried by 12 men across almost any terrain a man could march over.
Part of this was because Japanese Artiller designers erred on the side of 'unsafety' in that rather than build very robust carriage, mounts and thick gun barrels, they tried to get away with the bare minimum (in part because of a lack of steel which the navy consumed massive amounts of).
Finally, because they were fighting the Manchurians and Chinese with very limited numbers of guns of their own, the Japanese Army in Manchuria and China never needed larger guns. In fact if one looks at the lists of equipment the vast majority of guns are only up to ~75mm, ~105mm and their 'heavy guns in number' are only 150mm.
What can be said further about some of the Japanese Guns of the era is that they were designed so that should roads be available they had the sprung suspension and robust carriage for towing. As OTL progressed, that wasn't all that important, but the Japanese had experimented during the pre-war period in truck towed artillery fairly extensively. But like aforementioned, where there wasn't roads, you can't tow guns.
In this sense the terrain dictated what kinds of guns the Japanese could use, hence the guns that ended up being produced were precisely the ones that were mobile. It's a more evolutionary selection process here again, rather than one of doctrine.
In terms of infantry tactics someone else has already ninja'd me, pardon the phrase. The Japanese were a 'light infantry force' in fact they lacked light support equipment everywhere, even though they viewed it as a 'direct arm of the infantry'. So far more emphasis was placed on manoeuvre, and overwhelming attack, than was on actually *ahem* fighting *ahem*.
Part of the trouble was that low level commanders would often 'freelance' their senior officers and actually conduct frontal attacks. This was an endemic problem, particularly during the Pacific campaign, not so much in China. But it effectively made the Japanese foot doctrine one of 'infiltration and shock attacks', the trouble being that 'Shock Attacks' would quite often 'go off' piece meal, or individual groups would spoil the who surprise/ambush exercise.
From the high commands point of view, what was often wanted was a war of manoeuvre simply to capitalise on their advantages.
In Manchuria this had worked, in China it didn't. Partly this was because the Chinese attempted to 'dig in' a lot, which required artillery to be brought up, and partially because the terrain was so poort that even the Japanese found movement and logistics difficult....espically when the countryside was itself hostile because of the Japanese attitude to the local Chinese.
Hence the Japanese found themselves with rather high attrition and a difficulty in actually making manoeuvre when lower commanders would disobey orders and choose some other target to advance on.
In some respects, the size of the Japanese forces was a hindrance here, and it goes without saying that the firebrand middle officers, and low level 'disobedience' all culminated in that while the Japanese Army in China was mobile, it also lacked good co-ordination and was too 'opportunistic'.
At that said, being 'opportunistic' wasn't all that bad, since local commanders worked with what they had to get results even if they had nowhere near the proper logistics, manpower or support to conduct their 'freelancing'. If I may make my own analysis here, the Imperial Japanese got so much of a 'wanked history' because for the very reason that the actions were not controlled from the top.
Likewise, from my perspective of things, we give the Imperial Japanese Army too much credit for their 'battle tactics' since it was more commanders on the ground acting as they saw fit...not as the army saw things fit.
The force structure was appropriate for the time, China really was a 'Great War Era' campaign for Imperial Japan, the Chinese had large numbers, and the Japanese couldn't rely so much on manoeuvre compared to some of the Pacific campaigns. Which is why they had to maintain larger divisional sizes/outlays.
Bringing those last four paragraphs together, this is precisely why we see such 'pinning' manoeuvres in China, that look just like the early phase of the western front in the Great War, because the army units are 'WWI styled' and the tactics match (mcdo).
We see the initiative of local commanders to conduct raids against the stronger better organised allies, allied cohesion being broken up be repeated attacks from multiple low level Japanese commanders trying to organise an overwhelming attack, but it breaking up due to lack of co-ordination, and why we see opportunistic behaviour to press attacks such as unconsentual alludes to.
I am very much of the opinion, that the Imperial Japanese were a Great War power, trying to fight a modern WWII era war...hence they suffered terribly. That doesn't mean they were idiots, it doesn't mean that individual commanders were 'stupid', if anything many Japanese Commanders did tremendously with the very little equipment and adverse conditions they found themselves in. It is because of that, the Japanese were always reactionary to the place they found themselves in, hence overall strategy and tactics were lost on an armed forces that had to be flexible because of its structure and composition. In these aspects we really should admire the Imperial Japanese Army for how far it was able to get (i.e. Japano-wank in real life) rather than condone them as unequip idiots.
Yet for all that we can admire them, we do have to remember the brutal regime and actions of the Japanese and recognise that while they had a lot of potential to do well, there is only so far you can 'wank them' into being great conquerors. Coming back to the beginning of this summery, it is only in recognising why the Japanese were reactionary, and how they came to the point of having such a brutal regime and outlook that really one can begin to understand how this all came to be.
I am saying, if IJN leadership believes the Navy is under threat for its survival, it will act to prevent that.