Just read "An Introduction to Planetary Defense: A Study of Modern Warfare Applied to Extra-Terrestrial Invasion" (whew -- long title) by Travis S. Taylor. I must congratulate the author on writing about a subject that is seldom spoken of these days: What will we do if extra-terrestrials come calling? As someone who always felt how foolhardy it was to launch something into space with our home planet drawn on it -- obviously the people behind the launch never read what happened when Europeans "discovered" the Americas -- it was nice to know that others have taken our own history into account.
That said, I found parts of the book too abstruse for my taste, due to its diagrams and...equations (?), so I skimmed over them. I must also state that it's hard to make plans for planetary defense when you don't know what the aliens even look like, what their technology is like, or what their strengths and weakenesses might be. Still, it's comforting to know that the United States government has made plans -- I didn't know that before, although my impulse was to laugh when I heard about it -- however nebulous. It's true that these people will be immediate and high demand when a "first-contact" occurs (if they can shoulder the politicians out of the way, should it be a "friendly-alien" scenario).
The major piece of advice I took from the book was, that in case of hostile aliens attacking, your best bet is to do about the same thing you would do before a nuclear attack: get at least 200 miles away from any major population centers. Okay....that makes sense, but it's a small piece of, admittedly, sensible advice to be gleaning after reading the entire b
In short, there just isn't enough known about extra-terrestrials to be able to lay much in the way of plans. It amused me to read this book, and it was an interesting thought-exercise, but I wouldn't read it again. This might be a decent "beach" read. More than that I cannot say.
Go. Read. Enjoy!