I first encountered the idea in fiction a few months ago reading "Sixteen Ways to Defend a Walled City" [1]. For those interested in this kind of thing, it is a

I first encountered the idea in fiction a few months ago reading "Sixteen Ways to Defend a Walled City" [1]. For those interested in this kind of thing, it is a fictional mashup of a variety of technical innovations when an engineer (the army core kind) is the highest ranking military officer left during a siege. [1] https://www.goodreads.com/book/show/37946419-sixteen-ways-to-defend-a-walled-city https://www.goodreads.com/book/show/37946419-sixteen-ways-to...