Irish Medieval Units:
http://fanaticus.org/DBA/armies/IV58.html
Usually the Irish are treated as an afterthought in the game or the mods. Of course we know that the opposite was true and that they didn't just get absorbed by England at all. For a diverse number of reasons, once Northern Ireland was invaded, English occupation took hold. But of course they met beautiful Irish women and grew attracted to the culture, much like the Poulains of France in the Holy Lands grew attached to Muslim culture and learning.
If you find any other historical articles add them here. Of course liberties have been taken with all the units as it is a computer game mod, for balance and diversity of units.
I think the article is great because it helps us realize that the kingdoms and the units that fought there were not seperate, but evolved as a result of the influx of culture from diverse places and clans going back to the Dark Ages and Viking Raiders or the indigenous peoples.
De Militari
http://www.deremilitari.org/
Many peer reviewed articles of diverse medieval units. Often they will release portions of books being published. An excellent site that includes primary sources, but of course the source may have been a monk or a noble that didn't actually fight the battle but was an eyewitness.
I didn't put a Celtic Christianity web link since this isn't a spiritual site, but it would be well worth your time to do some research in it. Early missionaries traveled to the area, but then were forgotten by many of the initial senders. When far later missionaries arrived, there were surprised at the depth of the religion had penetrated the society and with effects of the indigenous belief systems creating a melange of beliefs and their own unique ways. All of these had effects on the military and the kingdoms. This difference in evolved Christianity resulted in an us versus them in Western Europe. All that plays out in later conflicts over and over.
The ORB: an encyclopedia of medieval studies:
http://www.the-orb.net/encyclo.htmlMany diverse medieval studies from an academic perspective