Samuel Hawley states in his book “The Imjin War” that the Japanese brought virtually no dedicated cavalry in their invasion of Joseon. I find this very surprising, though I could just be projecting a modern view of combined arms warfare on a preindustrial army. I’ve also seen it stated that the Japanese did bring some small cavalry contingents that were a minute part of their forces, mostly fighting as mounted infantry. I do know that the logistical burden of being horses across the Korean straight would be heavy, and that the the mountainous terrain of Korea like central Japan doesn’t lend itself well to cavalry maneuver. I also understand that the mounted samurai as battle winners had been pretty much replaced by musket armed ashigaru infantry backed up by more traditionally armed ashigaru and samurai infantry forces (bow, sword, and spear) decades before. I also understand that Japanese cavalry had performed poorly in the later stages of the Sengoku wars and compared to the musket and traditional armed infantry were much more expensive, harder/took much longer to train and were less effective. I also know that large Korean mounted archer formations from the northern border conflicts with Jurchen were heavily defeated by the Japanese in the initial battles of the invasion.
Had the Japanese abandoned cavalry tactics and formations so thoroughly by this time they left them out of their largest military operation up to that point? I had sorta equated the Japanese army at the time to the pike and shot formations of the west, though western armies still made use of cavalry. Did I just misunderstand Hawley or am I missing something fundamental about Japanese warfare in this period?
I have my problems with Hawley, but that aside...
So since you already know that cavalry, at least cavalry alone, would have faired badly in Korea (the Koreans found out the same) I will be brief.
The Tachibana/Takahashi contingent's mobilization order survives and it's rare to find such a detailed muster. It states
This means 5% of 3,000 men were expected to fight mounted. This is slightly lower than what we find in the Sengoku and in Edo-era regulations, but they were definitely there. While it's possible the lower percentage is due to having to cross the seas, it's also possible this contingent is just not representative, so keep that in mind.
According to the Annals of the Joseon Dynasty, in 1596 the Koreans decided to try to train themselves on the battle formation of the Japanese, so they decided to ask a Japanese who surrendered and became employed by the Korean army. As he describes, at the front were placed the flagbearers, and behind them the gunners, and behind them those wielding spears and swords. And on the two sides were placed "surprise forces". Once battle commence, the flagbearers will pull to the two sides, the gunners would fire, and on that impulse of attack those with spears and swords would charge forth and form up to the left and right. The flag bearers would then further flank the two sides as ambush and try to surround and harass the rear.
We know from examples recorded elsewhere in the Annals that "surprise force" could be composed of mounted warriors ("surprise force" is also pronounced the same way as "cavalry") but it's not a given. However it's probably fairly safe to assume that the mounted samurai would make up part of the "surprise force", the rest likely composed of squires on foot, as their location makes sense for where we'd find the horsemen and there's no explicit mention of horsemen in the description. Also while their existence is confirmed their role is not described, meaning they were likely supposed to cover their deployed area and act as a reserve if needed to plug or exploit. a doctrine which mirrors Japanese Edo-era military manuals (though in them the cavalry was deployed behind, not to the side, of the infantry). I would hazard a guess that it's recorded as "surprise force" and not "cavalry" because in general the foot squires were expected to deploy and fight beside their mounted masters. But again that's just my guess.
Does the existence of men who were expected to fight mounted count as "dedicated cavalry?" Well one, we should remember samurai are knights and like their European counterpart were also expected to fight dismounted should the situation call for it (heck even the Mongol horsemen fought dismounted when needed), but knights are still usually labeled as cavalry. Two, there were many cases recorded in Europe of commanders mixing light foot with their horsemen for both staying power and tactical flexibility to great effect, and to use an admittedly not very good comparison even today infantry are supposed to fight with and protect the tanks, but these are still usually labeled as cavalry. However it is true that there were no masses of horsemen-only squadrons making up a dedicated cavalry formation thousands of horsemen in total that you'd expect to find on a normal early-modern European battlefield. So you decide.