Actually the link below has been changed but still works. It first takes you to an article called "retreat security, I am your worst nightmare." by Jeff T. It is an eye opening read for those of you who plan on holding where you are (bugging in). . at the very bottom of the page you will find additional links which include; "The defense of Duffer's drift". It is actually a dated (1905) Army training short story. This little booklet was my first attempt at studying perimeter defense. It's a captivating narative that lets you live vicariously through the man who makes the mistakes -- then you get to see how the defense is improved iteratively. It was published in 1905 so the English/terminology takes some thought and, sometimes, a dictionary. It was found on SurvivalBlog in a great guest article (link) describing retreat security from the villian's point-of-view. One of the links given for further reading by the author (Jeff T -- probably Jeff Trassel) was the above booklet of maybe 40 pages (The Defence of Duffer's Drift). There were also other links of interest that also look quite helpful. I've read it one time already, but I've got a thick skull that needs refreshing quite often to remember anything.