The term 'Archduke' refers to a royal title given to members of the Habsburg dynasty, which was the ruling family of the Austro-Hungarian Empire from 1867 until its dissolution in 1918. The crossword solutions for the term Archduke are 'TRIO' (4 letters), 'AUST' (4 letters), and 'SARAJEVO' (8 letters). 'TRIO' is likely referring to the three Archdukes of Austria, Franz Ferdinand, Karl Ludwig, and Otto, who were all members of the Habsburg dynasty. 'AUST' is likely referring to the Austro-Hungarian Empire, which was ruled by the Habsburg dynasty. Finally, 'SARAJEVO' is likely referring to the assassination of Archduke Franz Ferdinand in Sarajevo in 1914, which is widely considered to be the event that sparked World War I.