In his new book, "On Desperate Ground," author Hampton Sides recounts the fateful experience of U.S. Marines and their clash with overpowering Chinese forces at the Chosin Reservoir in North Korea in November 1950, which has been called the Korean War's greatest battle. National security correspondent David Martin talks with Sides; Joint Chiefs of Staff Chairman Gen. Joseph Dunford, whose father fought at Chosin; and Warren Weidhahn, who was a private during the battle.