Semper Sci-Fi

I've been on a bit of a military sci-fi kick of late, and, though of course I'm no expert and can't claim to have read even a goodly portion of what's out there, I have noticed a trend in what I have read: military sci-fi seems to have a very large body of work by and/or about Marines. Have I just read a skewed sample, or am I on to something? Any more dedicated sci-fi fans care to confirm or refute my impression? And if it is a correct impression, what is it about Marines that attracts them to writing sci-fi, or attracts others to write sci-fi about them? Any insights from current and/or former Marines (if there are any in the audience)? Scott?

Speaking of Marine-centered military science fiction, the best of the bunch I've read lately are this series of books by Steven L. Kent about a future where Marines are clones. Told in the form of a memoir or autobiography, it's clear, crisp prose, solid world-building, and well-paced plotlines make it a thoroughly entertaining, and occasionally thought-provoking, read. The gender politics are little less progressive than one would want (basically, there are no women in the books, and what ones there are aren't exactly empowered or anything other than cardboard cut-outs with boobs), but overall highly recommended.