Oscarsborg Fortress is best known for sinking the  German heavy cruiser named for the Prussian victor of what?
Oscarsborg Fortress Oscarsborg Fortress (Norwegian: Oscarsborg festning ) is a coastal fortress in the Oslofjord, close to the small town of Drøbak. The best known part is situated on two small islets. The main artillery batteries are on the island Håøya and smaller batteries on the mainland to the west and east in the fjord and was military territory until 2003 when it was made a publicly available resort island. The fortress is best known for sinking the German heavy cruiser "Blücher" on 9 April 1940. In 2014, Oscarsborg Fortress was given protected status, effective from 9 April that year.
Hans von Koester Hans Ludwig Raimund von Koester (29 April 1844 – 21 February 1928) was a German naval officer who served in the Prussian Navy and later in the Imperial German Navy. He retired as a Grand Admiral.