Today in 1917 [July 17th] the British Royal Family, in a proclamation issued by George V, adopted the name of the House of Windsor in place of their German family name of Saxe-Coburg and Gotha due to the anti-German sentiment at the time.
He and all his British relatives relinquished their German titles and styles, and adopted British-sounding surnames. George compensated his male relatives by creating them British peers. His cousin, Prince Louis of Battenberg, who earlier in the war had been forced to resign as First Sea Lord through anti-German feeling, became Louis Mountbatten, 1st Marquess of Milford Haven, while Queen Mary’s brothers became Adolphus Cambridge, 1st Marquess of Cambridge, and Alexander Cambridge, 1st Earl of Athlone. George’s cousins Princess Marie Louise and Princess Helena Victoria of Schleswig-Holstein dropped their territorial designations.