5 changes to castle building in the medieval period

[Imperial Dave]

Five Game-Changers in Medieval English Castle-Building - Medievalists.net https://share.google/PPK0nIHVITCYzsMMi

Not overly detailed but hopefully of interest

[Nick Harbud]

For anyone wanting to know more about medieval castle design development, as well as the reasons for building (or laying siege to) castles in particular locations, this book might be of interest.

[Erpingham]

Because it is a short filler piece, it has treated English castles in isolation, which is a mistake because there are international trends in play, as Nick points out.  The English just followed trends on circular/polygonal towers and concentric design, for example.

[Imperial Dave]

Very true and alot of the late Roman stuff could be classed as castles...