In 1940, native West Texan Roy H. Elrod joined the Marine Corps. A few years later his unit, the 8th Marine Regiment, went into the fight at Guadalcanal, where he commanded a platoon of 37 mm gunners. They endured Japanese attacks, malarial tropical weather, and starvation rations. His combat leadership earned him a Silver Star and a battlefield promotion.

On D-Day at Tarawa his platoon waded their 37 mm cannons ashore, each weighing nearly 1,000 pounds, through half a mile of bullet-laced surf to get to an island where the killing never stopped. His was the only platoon to get its guns...