Im sorry I don’t know where else to ask this. I want to learn about fort design, construction what features made them effective, how they changed over time, strategic locations (geography) like hills, who used them... and more. Where do I look? Any books videos or online resources? I tried google but thats been less than helpful
I'm not sure whether his works are out of date by now—I'm not a military historian, so I don't really keep current on these things—but I recall the works of Christopher Duffy being pretty helpful as far as early modern European fortification. (Especially his two-volume Siege Warfare and the more condensed Fire And Stone: The Science of Fortress Warfare 1660-1860.)
Another book that's certainly out of date, but still might be useful is E. Viollet-le-Duc's Annals of a Fortress, which is also interestingly formatted—rather than taking a textbook approach to the history of fortifications, he tries to demonstrate it through a fictional history of a fictional fortress!