Sophie, Duchess of Hohenberg
Sophie was the wife of Archduke Franz Ferdinand. (PROSE: The Whoniverse) was assassinated alongside her husband, Archduke and heir to the Austrian throne, in Sarajevo, Bosnia (PROSE: Human Nature) on 28 June 1914. (COMIC: The Dalek Project)
The Archduke and his wife were killed by Gavrilo Princip, a Serbian nationalist protesting Austria's claims on Sarajevo and the rest of Bosnia, territories the Serbs believed were rightfully theirs. (PROSE: Human Nature) Ferdinand's death led directly to the First World War, "through nations having treaties with nations", according to the Tenth Doctor. (TV: The Family of Blood)
While investigating the Dalek Project the Eleventh Doctor grew fearful as he began to suspect that the Daleks had engineered the assassination of Ferdinand and his wife by conditioning Princip to kill them and thus plunge the world into war, although his suspicions were never confirmed. (COMIC: The Dalek Project)