"Gates of Fire" by Steven Pressfield
I am almost done with this book. It is a very entertaining book about the 300 Spartans and a few thousand Allies last stand against 250,000 Persians at the choke point called Themopylae(Hot Gates)in 480BC. It's fiction, but very well written. It captures the "Warrior Ethic" very well. I highly recommend it. The language can be crude in a "one of the boys" sense.
“Out of every one hundred men, ten shouldn't even be there, eighty are just targets, nine are the real fighters, and we are lucky to have them, for they make the battle. Ah, but the one, one is a warrior, and he will bring the others back.”Heraclitus