The two-week fight at the Chosin Reservoir was one of the decisive battles of the Korean War – and one of the seminal moments in the history of the Marine Corps. We talk with historian Hampton Sides about the courageous Marines who braved sub-zero temperatures to fight a battle in which they were seriously outnumbered. Sides tells their story in “On Desperate Ground: The Marines at The Reservoir, the Korean War’s Greatest Battle” (Doubleday).