At the beginning of World War II, the devastating impact of German submarines on both the Royal Navy and merchant shipping saw Britain on the brink of starvation and defeat. Here Michael FitzGerald recounts the story of how the Allies redressed the balance of power, with the eventual result that the elite U-boat crews suffered the heaviest losses of any branch of the German services: out of 40,900 men, 28,000 were killed and 5,000 taken prisoner; by 1945, the average age was 19 and the survival rate was only three missions.