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. Oscarsborg Fortress:  The fortress is best known for sinking the German heavy cruiser "Blücher" on 9 April 1940. German cruiser Blücher: Blücher was the second of five "Admiral Hipper"-class heavy cruisers of Nazi Germany's "Kriegsmarine", built after the rise of the Nazi Party and the repudiation of the Treaty of Versailles. German cruiser Blücher:  Named for Gebhard Leberecht von Blücher, the Prussian victor of the Battle of Waterloo, the ship was laid down in August 1936 and launched in June 1937.
the Battle of Waterloo