Military historian Brenner (We Were One: Shoulder to Shoulder with the Marines Who Took Fallujah) brings a cinematic style and considerable expertise to this engrossing tale of a behind-enemy-lines mission during the last year of WWII. Conducted by the Office of Strategic Services (OSS, the predecessor to the modern CIA), the plan was to cut ""a carotid artery of the Third Reich,"" the infamous Brenner Pass through the mountains between Austria and Italy, leaving the German army in Southern Italy isolated. Arguably one of the war's most dangerous operations, it was led two OSS operatives who never met: Stephen Hall, a combat engineer trained in demolitions, who conceived and sold the plan (and himself) to the newly formed OSS; and Howard Chappell, a Fort Benning paratroop trainer recruited by the OSS to train the team of ""shadow soldiers"" who would infiltrate Nazi Germany under Hall's command. Unfortunately, the main theater of operations had shifted to France by the summer of 1944, and the team was shorted critical logistical support. With thorough research and new interviews, O'Donnell provides an insightful look into the internal struggles of the burgeoning OSS as well as a real-life espionage adventure of bravery, ingenuity and sacrifice.