シュレースヴィヒ＝ホルシュタイン問題
In the early 19th century, the Danish royal line started to go extinct. The Duke of Augustenborg was the next male-line heir to the royal house, though not descended in male line from Frederick III of Denmark and Norway. This made the duke a player in the convoluted Schleswig-Holstein Question, as well as a candidate in the Danish succession. Frederik August of Augustenborg attempted to proclaim himself reigning Duke Frederick VIII of Schleswig-Holstein in 1864, upon the final extinction of the senior branch of the Danish kings. His daughter, Augusta Victoria of Schleswig-Holstein, became German Empress as consort of Wilhelm II.