Birger Eriksen

Birger Kristian Eriksen was a Norwegian officer who was instrumental in stopping the first wave of Gruppe 5 of the German invasion force outside Oslo.

Eriksen was the commander of Oscarsborg Fortress when Nazi Germany attacked Norway in the early hours of 9 April 1940. He gained lasting recognition for ordering the fortress under his command to open fire on the vanguard forces of Operation Weserübung, sinking the 16,000 ton heavy cruiser Blücher.

Source: Wikipedia