The Special Operations Executive (SOE) was one of the most innovative British creations of the Second World War. Its mission was to export resistance, subversion, and sabotage to occupied Europe and beyond, disrupting the German war effort and building a Secret Army which would work in the shadows to help defeat the Nazis. Potential agents were put through intensive paramilitary and parachute training, then taught how to live clandestinely behind enemy lines, to operate radios and write in secret codes. They lived in constant fear of arrest, and of betrayal by treacherous collaborators. This...