Torpedo battery
Concealed underwater torpedo battery that sank the Blücher.
The Oscarsborg torpedo battery was built into a cave carved out of the rock on Nordre Kaholmen island. Construction ran from 1898 to 1901, and it became operational on 15 July 1901. It was one of only two such facilities in Norway, and it stood apart from the other one at Kvarven Fort near Bergen because its torpedoes were launched from below the waterline rather than from an above-ground tube. The battery remained a secret from German intelligence right up to the invasion on 9 April 1940.
Inside the concrete structure, two torpedoes sat side by side in open steel frames. One frame could be lowered like an elevator into underwater tunnels. After firing, swapping the frames for a second shot took time. The battery had three torpedo tunnels, each holding one torpedo at a time, allowing only three torpedoes to be fired without reloading, and a total of six were typically stored (one in each tube and one in reserve per tunnel). Each torpedo carried a 100 kg gun cotton warhead. Spotters watched from three observation bunkers above the battery, with a backup bunker near the entrance. The torpedoes themselves were delivered in 1900 from the Whitehead Torpedo Works in Fiume, then part of Austria-Hungary.
Quick Facts
- Location
- Drøbak Sound, Oslofjord, Norway
- Controlled By
- Norway / Nazi Germany (1940–1945)
- Built
- 1846–1855
- In Use
- 23 August 1855 – 28 June 2002
- Battles
- Battle of Drøbak Sound
- Past Commanders
- Oberst Birger Eriksen
Facts from the source article.
Lore & Background
The torpedo battery is a concrete construction inside a cave mined into the rock of Nordre Kaholmen island. Two torpedoes are loaded side by side in two open steel frames; one frame is then lowered like an elevator into the water to the tunnels below. After one shot, it took time to swap frames and be ready for the next. When fired, the torpedo's own compressed air engine started and propelled it. The battery has three torpedo tunnels, each holding one torpedo at a time, so only three torpedoes could be fired without reloading, and a total of six torpedoes were typically stored and ready for use (one in each tube and one in reserve per tunnel). Each weapon carried a 100 kg gun cotton warhead, and targets were spotted from three observation bunkers just above the battery, with a back-up observation bunker just outside the entrance. The torpedoes were delivered in 1900 from the Whitehead Torpedo Works in Fiume, then part of Austria-Hungary.
During the Cold War, the underground torpedo battery remained secretly active up until 1 January 1993, having been modernized in the 1980s. After the deactivation of the last weapon systems, the remaining military activity on Oscarsborg consisted of the Coastal Artillery officer training programme, which was officially closed on 28 June 2002.
Reader's Guide
The Oscarsborg torpedo battery is significant for its role in the defense of Oslo during the German invasion of Norway on 9 April 1940. Its concealment from German intelligence allowed it to operate effectively, firing two torpedoes that struck the heavy cruiser Blücher, contributing to its sinking. This action delayed the German naval force heading for Oslo, preventing the Norwegian King and government from being captured. The battery's design—launching torpedoes from under water level—was unique in Norway at the time. Its continued secret operation through the Cold War until 1993 underscores its lasting strategic importance. The battery is now part of the Oscarsborg Fortress Museum, a publicly available site, and the fortress was listed as a protected site in 2014.
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