United States in World War I
Admiral Sir William Reginald Hall (28 June 1870 – 22 October 1943), known as Blinker Hall, was the British Director of Naval Intelligence (DNI) from 1914 to 1919. Together with Sir Alfred Ewing he was responsible for the establishment of the Royal Navy's codebreaking operation, Room 40, which decoded the Zimmermann telegram, a major factor in the entry of the United States in World War I.