Gates of Fire — Steven Pressfield

At Thermopylae, a rocky mountain pass in northern Greece, the feared and admired Spartan soldiers stood three hundred strong. Theirs was a suicide mission, to hold the pass against the invading millions of the mighty Persian army. Day after bloody day they withstood the terrible onslaught, buying time for the Greeks to rally their forces. Born into a cult of spiritual courage, physical endurance, and unmatched battle skill, the Spartans would be remembered for the greatest military stand in history--one that would not end until the rocks were awash with blood, leaving only one gravely injured Spartan squire to tell the tale....