Maurice Isserman is a historian and author. A professor at Hamilton College, he's written many notable works, including the mountaineering histories, "Falling Giants," "Continental Divide: A History of American Mountaineering" and a biography of Michael Harrington called, "The Other American." Grant Reeher speaks with Isserman about his new book, "The Winter Army: The World War II Odyssey of the 10th Mountain Division, America's Elite Alpine Warriors."