The Allied advance was stopped, rumor had it that die-hard Nazis would take a stand in the Alps if the front collapsed: it was time, the OSS command decided, to start infiltrating agents into Germany for eye-witness information that Ultra, intercepting messages, couldn't provide. Thanks to the declassification of OSS documents and extensive interviews with survivors, Persico (My Enemy, My Brother, 1977) has been able to reconstruct this operation in stunning detail from the first purchase of refugee clothes in New York three years before-clothes that would eventually pass Gestapo scrutiny as German-made. In London, under the unprepossessing, magnetic Wild Bill Donovan, two irregular Army privates manufactured cover stories (the color of local streetcars, for instance, was a stock Gestapo query to trap suspects) while the Labor Division recruited refugee workers with Socialist trade-union connections. In Berne, the unflappable Allen Dulles--a late arrival in Switzerland before it was sealed off--gathered intelligence from anti-Nazi German officials Hans Bernd Gisevius, a conspirator in the plot to assassinate Hitler, and ""bureaucratic drone"" Fritz Kolhe, who deposited Foreign Office cables in the Americans' lap. Others put their lives on the line from different motives--like patriot Fritz Molden, who created the Austrian resistance movement he claimed existed in order to place Austria on a respectable footing after the war; and White Russian Ã‰migrÃ‰ Youri Skarzynski, who coolly passed himself off in SD (Nazi Secret Service) headquarters as the first SD agent to return since the fall of France. Whether the secret penetration of Germany-which the British had always opposed--actually shortened the war by a single day is, as Persico notes, unknowable; but it emerges--in this deft, acritical narrative--as a considerable accomplishment and one of the brighter episodes in U.S. espionage history.