During World War I Franz Joseph served in Germany's Kaiserliche Marine ("Imperial Navy") as the second torpedo officer on the light cruiser "SMS Emden" at the Battle of Cocos. The "SMS Emden" had an extraordinary record capturing British ships, and as a result all those who served on her, including Franz Joseph, were given the right to add the ship's name to the end of their surnames. Since Germany had converted titles of nobility into family names in 1919, he became Franz Joseph Prinz von Hohenzollern-Emden.