A natural cave had been enlarged and enhanced with three chambers loaded with torpedoes produced in Rijeka, Croatia.
The Blücher unwittingly passed with 500 m of the torpedo battery. Two torpedoes were launched towards the target. What followed were some of the most dramatic hours in Norwegian history.
The torpedoes sunk the ship and simultaneously severely damaging other ships in the German fleet. This delayed the Germans' arrival to Oslo. It allowed for the King, his family and the government to avoid captivity and continue to run the resistance from exile in London.
All made possible because of torpedoes from Rijeka.
This drama is captured in the movie “The King’s Choice” directed by Erik Poppe. Read more about the events on Wikipedia.