Monaco Succession Crisis of 1918

The Monaco succession crisis of 1918 arose because France objected to the prospect of a German national inheriting the throne of the Principality of Monaco. Prince Albert I had only one legitimate child, the Hereditary Prince Louis, then heir apparent to the principality. As World War I drew to a close, Prince Louis, at the age of forty-eight, remained (legally) childless, unmarried, and unbetrothed.

Louis' nearest legitimate next of kin was Prince Albert I's first cousin Wilhelm, 2nd Duke of Urach (1864–1928). He was born in Monaco in 1864, and was largely raised there as a Francophone Roman Catholic by his mother after her widowhood in 1869. He was, however, a Kingdom of Württemberg national, and his adult domicile and main assets (including Lichtenstein Castle) were in Württemberg. Although he was awarded the Grand Cross of Monaco's Order of Saint-Charles and was a knight of the Sovereign Military Order of Malta, he also held the Grand Cross of the Order of the Crown of Württemberg and was a knight of Kaiser Wilhelm II's Order of the Black Eagle. In 1871 Württemberg became a part of the German Empire, and by 1911 this coloured the status of Wilhelm's claim to Monaco.

...
Wikipedia