The strange, forgotten World War II mission that involved Americans and Nazis cooperating to save a rare breed of prize horses from extinction. It was late April 1945 when the Americans first heard about the white horses. It happened near the Czech-German border, about 90 miles east of Nuremberg. Capt. Ferdinand P. Sperl, an officer with IPW (Interrogation Prisoners of War) 10, was examining a cache of items he’d just confiscated from a Nazi colonel known only as “Walter H.” They were typical intelligence documents: memos, maps, charts. But something in the colonel’s personal attaché case caught Sperl's eye: photos...