It appears that the US Army has gotten too relaxed after 20 years of living on Forward Operating Bases (Starting in Somalia). The logistic and security posture/doctrine these days are based on these brigade-sized FOBs. (If the Army still has an institutional security doctrine anymore.) To the extent that the Division staff (and above) think about security, it is from the stand point of Anti-Terrorism/Force-Protection. Maybe the Infantry School (& Ranger School) is still teaching tactical security and patrol base defense, but most Army officers have no training on this subject beyond that FM 7-8 (http://www.globalsecurity.org/military/library/policy/army/fm/7-8/index.html) they're supposed to read on their own. If you're one of these unfortunate officers, I urge you to pick up a copy of Millen's "Command Legacy" http://www.amazon.com/Command-Legacy-Tactical-Leaders-Revised/dp/159797207X/ref=sr_1_1?ie=UTF8&s=books&qid=1256222637&sr=8-1 . It's a great book filled with concrete TTPs and discussions. You have a defense plan that you can pick up from the book to use, and he explained all of his reasons so you can adapt it on your own. Even infantry officers will get a lot out of this book. Granted, Millen's chapters on defense are based on a Mobile Defense, where you have a Battalion Reserve to come save you. On the other hand, in a patrol base defense like Wanat & Keating, you site your positions around the center, and have a parameter wall. The basic principles are the same.
As we go into the world of Resilient Communities, some of you may find the need to brush up on defensive planning. Millen's book is an excellent starting point. Just remember that you need at least a platoon of people to defend your hamlet.