The Royal Navy’s strategy in the Second World War, just as it had been in the Great War, was to protect the British Isles from attack, to keep the islands vital sea supply lanes open and to maintain communication with the far-flung British Empire and Allied forces fighting in distant theatres. From the early sinking of the pocket battleship Graf Spee in December 1939, through the Norway campaign, the Dunkirk evacuation in 1940, and the sinking of the Bismarck in 1941, the senior service more than played its part. It was aided by technological development such as the development of radar and Asdic, the echo sounding device for detecting submarines. Indeed, its greatest challenge lay under the waves, in countering and finally defeating the U-boat threat to our crucial food imports in the Battle of the Atlantic. Meanwhile, the loss of the Prince of Wales and Repulse to Japanese bombers, and the Battle of Midway in which Japan lost three Aircraft Carriers to the US, sounded the death knell for a century and a half of Britain’s maritime supremacy. Even so, she ended the war still possessing by far the world’s largest fleet.