/u/hborrgg asked a question a couple of weeks ago on the useage of spears and shields, and I've been trying to provide a medieval perspective ever since. This was already on my mind because it relates to a question on the Battle of Hastings I've been trying to answer for a couple of months, but I haven't made much headway. In spite of the considerable amount written on how Ancient Greek hoplites fought down to an individual level and some acrimonious debate over whether cavalry or infantry dominated the medieval battlefield, there doesn't seem to have been any discussion as to how the medieval footsoldier fought. The closest I've come to the subject is Verbruggen's analysis of the psychology of medieval cavalry and footsoldiers.
Now, due to the differences in shield design and quite possibly also spear and sword design, research into the hoplite phalanx is of limited use when considering the medieval period (perhaps excepting Van Wees and his adherents, but I haven't had a chance to read him yet), which is why I'm wondering if perhaps there's a study or a book that I've missed which deals with the topic I'm interested in.
There is quite a lot written on that topic as well. Not only that but there are even many people who try to recreate the way people in the Middle Ages fought. We can actually do this (to an extend) because there are a number of fencing treatises surviving from that era - i.e. the earliest known such manuscript is the so called I.33 or the Tower fechtbuch, dating to the early 14-th century. This one outlines the ways one would use a buckler (a small shield, about 20-30 cm in diameter) in a combination with a sword. There are a number of more extensive manuscripts, starting from the early 15-th century, that cover different weapons and situations - form spears and poleaxes all the way to wrestling and fighting with daggers.
If you note however, these are mostly from the 14-15th century onward. Furthermore, they seem to be more focused on the self-defence and duel aspect, so things like what to do in a unit, or unit tactics are not really covered. Furthermore, shield use (barring I.33) is shown only in a judicial duel context or in manuals after the 1500s. For earlier periods, like the Battle of Hastings we have some contextual clues, but unfortunately not a lot of data - so most of the things we can learn about the way they fought that early is based on speculations, and extrapolations from the later manuals as well as from artwork and textual descriptions, like in the viking sagas.
Perhaps the greatest sources (for me), and active area of research are the various Strategikons from the Byzantine empire - these describe how to wage war, how to form an encampment and what tactics to use against different foes (i.e. how to fight the bulgars (hint - don't get caught in a mountain pass) or the arabs and so on). However, these do not cover individual combat, and while some things are bound to be common, you can't really directly apply that knowledge to Western Europe.
As a side question, are there any particularly useful sources that you've come across on hoplite warfare? Sorry if its slightly off topic, I'm writing a dissertation on Philip II's reforms of the Macedonian military and the resulting changes in hoplite warfare but I've not found as many sources as I'd like