My goal here is to provide some glimpses of medieval history that might be useful for writers. Today I want to talk about castles. Castles weren’t one thing. They came in all kinds of shapes and sizes, from simple fortified keeps to motte and bailey constructions, through multiple concentric rings of defences, to the over-elaborate fantasies of Mad King Ludwig of Bavaria. Commonly, we tend to think of castles as a Norman introduction to Britain, and they certainly made the most of them. Yet if we think of a castle as simply a fortification with some living space, we have forts dating back to the Romans and before.
What were castles for? Defence is an obvious answer, but actually, there are many examples of country houses with castle-y features like moats or crenulations, but which would never function defensively. They might be overlooked, or lacking in real walls, or any one of a dozen other things. In these cases, castles were more about projecting authority and status. They were a big staple in the countryside, saying “I own this”. They were also a way of saying that the owner was of a level of nobility that allowed them to build castles.
Some kings required the building of castles (religious institutions only sometimes being exempt from the obligation), while others required licenses to build them. For a writer, that could provide a useful source of ongoing disputes with authority, if you need them. At the very least, you should consider doing something more than just a big ring of walls with a tower the next time you need a castle.