By the summer of 1940, Hitler had conquered much of Europe and turned his attentions to England. The Germans hoped to use their U-boats to create a naval blockade of the island that would soon starve Britain into surrender. Nazi submarines sank ships carrying food, supplies, and, in one notorious instance, numerous civilian children. Sensing defeat imminent, Captain Gilbert Roberts devised an ingenious solution. Assisted by female volunteers from the Women’s Royal Naval Service (“Wrens”), he created a strategy game that allowed the Navy to map out tactics for defeating the Germans at sea. This is an engrossing true story engagingly told, full of vividly drawn supporting characters and no lack of suspense.