Marlene Dietrich made her way to a recording studio in the middle of New York’s Times Square, about to give one of the most audacious performances of her career. The Berlin-born screen siren had renounced her German citizenship five years earlier, and become a proud American - a move that had so enraged Hitler, he’d put a seven-figure bounty on her head. But Dietrich was undeterred, and went on to become a key figure in the US war effort, singing for Allied troops in Algeria, France, Italy, and Germany - often in extremely dangerous conditions. What is less well-known is...