Yes, they did - and quite extensively, even. More can always be said on the matter of the Anglo-Saxon burh, so if anyone else wants to have a go at it, please don't let this post stop you! We never turn down new material. For the meantime, we have quite a bit of existing posts on just this matter, mostly by u/BRIStoneman:

• On the nature and function of the burghal network;
• On the construction and nature of their defences;
• On why some places became burhs and why others didn't;
• On how they used beacon fires like you saw in the LotR films.

And they even provide their PhD thesis on the burh system as it was in Mercia in that first link. (It's titled "Mutually Assured Construction", at which point I had to grab the thing. Oh god, my backlog.)