There wasn't a thing Ernest Shackleton could do. He stood on the ice-bound Weddell Sea, watching the giant blocks of frozen saltwater squeeze his ship to death. The ship's name seemed ironic now: the Endurance. But she had lasted nine months in this condition, stuck on the ice in the frigid Antarctic winter. So had Shackleton and his crew of 28 men, trying to become the first expedition ever to cross the entire continent. Now, in October 1915, as...