Photo: Kjetil Lenes·CC BY 2.5· Wikimedia Commons
Islands / Frogn / Nordre Kaholmen
The northern of the two Kaholmene islets that make up Oscarsborg fortress in Drøbaksundet. The torpedo battery that sank the German cruiser Blücher on 9 April 1940 stood here. Part of the fortress area open to visitors.
Nordre Kaholmen is the northern of the two Oscarsborg islets, the one closest to the Drøbak side. There is little to see beyond a low fortress wall and a few buildings, and that is the whole point. The weapon that sank the Blücher lay below the waterline here, invisible from the sea.
ferry from Drøbak.
Boats do run here, but the quay is not in Entur’s system — usually a summer service or a private crossing that never enters the national journey planner. Check with the operator before you build a day around it.
Nordre Kaholmen carried the torpedo battery, the thing that decided the morning of 9 April 1940. The battery was built between 1898 and 1901 and entered service on 15 July 1901, with three launch tubes below the water. The torpedoes came from the Whitehead factory in Fiume and carried a 100 kg warhead. The installation could fire six torpedoes without reloading, with nine ready for use.
When the Blücher passed in the dark, the guns on Søndre Kaholmen had already opened fire. Commander Andreas Anderssen, 65 years old, fired two torpedoes from the hidden battery. They hit the cruiser amidships. The Blücher lost steering, caught fire and sank some time later west of Askholmene. The battery had stood ready for almost four decades and was used once, on the occasion that counted.
The islet is otherwise part of the fortress complex, built out from the middle of the 1800s and modernised around the turn of the century.
Nordre Kaholmen is part of the Oscarsborg fortress area open to the public. The torpedo battery is preserved and is one of the high points of the museum site. The fortress was decommissioned as a military installation in 2002 and listed as a cultural monument in 2014.
Nordre Kaholmen is reached like the rest of Oscarsborg: ferry from Drøbak all year, or private boat to the guest harbour. The area is open to the public.
The torpedo battery was old iron by 1940, built around 1900, and it was this that did the job.
The tubes lay under water. A ship's captain sailing past saw nothing to fear.
Andreas Anderssen was 65 and strictly speaking too old for active service. He fired the two shots that changed 9 April.
Oslo Sea Experience passes Nordre Kaholmen on its private fjord trips from Tjuvholmen.
The Norwegian version notes which facts were taken from each source: Nordre Kaholmen på norsk.