From 1914 to 1918 Britain was at
war with
Germany. The German Emperor
Wilhelm II, who for the British public came to symbolise all the horrors of the war, was the King's first cousin. Queen Mary, although both she and her mother were British, was the daughter of the
Duke of Teck, a descendant of the German
Royal House of Württemberg.
The King's paternal grandfather was
Prince Albert of Saxe-Coburg-Gotha; the King and his children bore the titles Prince and Princess of Saxe-Coburg and Gotha and Duke and Duchess of Saxony. The King had brothers-in-law and cousins who were British subjects but who bore German titles such as Duke and Duchess of Teck, Prince and Princess of Battenberg, Prince and Princess of Hesse and by Rhine, and Prince and Princess of Schleswig-Holstein-Sønderburg-Augustenberg. Writer
H. G. Wells wrote about Britain's "alien and uninspiring court", and George famously replied: "I may be uninspiring, but I'll be damned if I'm alien."
On
17 July 1917, George V issued an
Order-in-Council that changed the name of the British
Royal House from the German-sounding
House of Saxe-Coburg-Gotha to the
House of Windsor, to appease British nationalist feelings. He specifically adopted Windsor as the surname for all descendants of Queen Victoria then living in the United Kingdom, excluding women who married into other families and their descendants.
Finally, on behalf of his various relatives who were British subjects he relinquished the use of all German titles and styles, and adopted British-sounding surnames. George compensated several of his male relatives by creating them British peers. Thus, overnight his cousin,
Prince Louis of Battenberg, became Louis Mountbatten, 1st Marquess of Milford Haven, while his brother-in-law, the
Duke of Teck, became Adolphus Cambridge, 1st Marquess of Cambridge. Others, such as
Princess Marie Louise of Schleswig-Holstein and
Princess Helena Victoria of Schleswig-Holstein, simply stopped using their territorial designations. In Letters Patent gazetted on
11 December 1917, the King restricted the style "His (or Her) Royal Highness" and the titular dignity of "Prince (or Princess) of Great Britain and Ireland" to the children of the Sovereign, the children of the sons of the Sovereign, and the eldest living son of the eldest living son of a Prince of Wales.
The Letters Patent also stated that "the titles of Royal Highness, Highness or Serene Highness, and the titular dignity of Prince and Princess shall cease except those titles already granted and remaining unrevoked." Relatives of the British Royal Family who fought on the German side, such as
Prince Ernst August of Hanover, 3rd Duke of Cumberland and Teviotdale (the senior male-line great grandson of George III) and
Prince Carl Eduard, Duke of Albany and the reigning Duke of Saxe-Coburg-Gotha (a male-line grandson of Queen Victoria), were simply cut off; their British peerages were suspended by a 1919 Order in Council under the provisions of the
Titles Deprivation Act 1917. George also removed their Garter flags from
St George's Chapel at
Windsor Castle under pressure from his mother, Queen Alexandra.
When
Tsar Nicholas II of Russia, a first cousin of George through his mother, Queen Alexandra (Nicholas II's mother was
Maria Fyodorovna, Queen Alexandra's sister) was overthrown in the
Russian Revolution of 1917, the British Government offered asylum to the Tsar and his family but worsening conditions for the British people, and fears that revolution might come to the British Isles, led George to think that the presence of the Romanovs might seem inappropriate under the circumstances. Despite the later claims of
Lord Mountbatten of Burma that
David Lloyd George, the Prime Minister, was opposed to the rescue of the Romanovs, records of the King's private secretary,
Lord Stamfordham, suggest that George V opposed the rescue against the advice of Lloyd George. Advanced planning for a rescue was undertaken by MI1, a branch of the British secret service, but because of the strengthening Bolshevik position and wider difficulties with the conduct of the war, the plan was never put into operation. The Tsar and his immediate family thus remained in Russia and were murdered by
Bolshevik revolutionaries in
Yekaterinburg in 1918.
Two months after the end of the war, the King's youngest son,
John, died aged 13 after a short lifetime of ill-health. George was informed of the death by the Queen who wrote, "[John] had been a great anxiety to us for many years…The first break in the family circle is hard to bear but people have been so kind & sympathetic & this has helped us much."