It was a split-second operation as delicate and as deadly as a time bomb. It demanded the concentrated devotion and vigilance of more than six hundred men for every hour, every day, and every night for more than a year. With only their bare hands and crude homemade tools, they sank shafts, built underground railroads, forged passports, drew maps, faked weapons, and tailored German clothes. They developed a fantastic security system to protect themselves...