So I was talking to a friend about (what little I know of) historical combat, and I noted how there is no place that I've seen any use of shields in Japanese military applications. This then leads me to several questions:
1 Would they have formation combat like in Europe?
2 How would the formations or surrounding units (skirmishers and archers, etc.) work, and would this be very different from Contemporary armies in other regions?
3 what is the main logic of the combat throughout this period? Was the focus on elite troop combat (samurai duels are the obvious example)?
Any insight into Japanese military doctrine and combat at this time would be very appreciated as well.
I don't know that much about this subject, I'm afraid, but I know that during the late Heian period (around the 12th century), at least, it was extremely relevant to warrior nobility to kill enemies of high standing, since they would receive a greater gift in lands and goods for their deaths. This made single combat an important part of battles. In martial narratives like the Heike monogatari we see the principal members of the clashing clans declaring their names when they are about to engage in combat. If they die, they are quick to ask their squires and underlings to inform their superiors of those foes they have killed, so their families can get their due payment.
Of course, these chronicles discuss mainly leading figures, so I don't know how the clans' saburai (word that at this point merely designates a servant or retainer) would live the combat. However, the name calling custom (nanori) was well established. I do not remember the name, but there is an illustrated scroll written around the time of the Mongol invasions, where the writer mentions the bafflement of the invaders when their enemies started announcing who they were.
It really depends on what era of "medieval" Japan you're talking about. IIRC, the Genpei War was fought mostly between horse archers (who were on rather small, slow moving horses) or I guess foot archers. Most battles started with archery duels and maybe sometimes went into hand-to-hand combat. Numbers were not huge in general.
Needless to say, things had changed a lot by the Sengoku Period, which is why Shogun Total War exists.