Photo: Kjetil Lenes·CC BY 2.5· Wikimedia Commons
Islands / Frogn / Kaholmane
Nordre and Søndre Kaholmen, the two islets that together are Oscarsborg fortress in the Drøbak sound. A national fortress with a museum, hotel, restaurant and opera festival, known for sinking the cruiser Blücher on 9 April 1940.
The two islets in the middle of the Drøbak sound, with the fortress walls, the whitewashed buildings and the guns, are Oscarsborg. This is the narrowest part of the sound, which is why the point was the most important barrier on the way in to Kristiania (now Oslo). The wreck of the Blücher still lies on the bottom just below.
ferry from Drøbak (year-round).
Times shift with the season, and several of the island boats run only in summer. Check the current timetable at Ruter.
Kaholmane is Nordre and Søndre Kaholmen, two islets that together make up Oscarsborg fortress. The main fort on Søndre Kaholmen was completed on 20 November 1848 and carried more than 100 guns through the 1850s. It was modernised from 1875 and heavily expanded between 1893 and 1901, when it got three 28 cm Krupp guns called Moses, Aron and Josva.
The decisive weapon lay hidden under water at Nordre Kaholmen: a torpedo battery with three submerged launch tubes, put into service on 15 July 1901. It fired Whitehead torpedoes from Fiume with a 100 kg charge.
On 9 April 1940 the German cruiser Blücher came up the sound in the dark, carrying the invasion force and the administration for the occupation. Commandant Birger Eriksen gave the order to fire without a warning shot. Two of the 28 cm guns opened up at around 04.21, and Commander Andreas Anderssen fired the torpedoes from the old battery. Blücher caught fire and sank west of Askholmene at around 06.23. Around 1,000 Germans died. The delay gave the royal family, the government and the gold reserve time to get away.
The fortress was decommissioned as a military installation on 28 June 2002 and is now a national fortress, protected as a cultural heritage site since 9 May 2014. There is a branch of the Norwegian Armed Forces Museum (Forsvarsmuseet), a hotel with around 190 beds, a restaurant and galleries. The Oscarsborg opera is staged every August. About 100,000 people visit the islands each year.
The ferry from Drøbak runs all year. Private boats can moor in the guest harbour. The museum and the outdoor areas are open to the public. The hotel and restaurant are operated commercially.
The three big guns were called Moses, Aron and Josva. Two of them fired that morning.
The torpedoes that sank the Blücher were almost 40 years old when they were used, fired by a 65-year-old officer from a battery most people thought was obsolete.
Eriksen never received a written order to shoot. He fired on his own responsibility, at a ship he did not know for certain was hostile.
Blücher carried the men who were to govern occupied Norway. Their going down here gave the king and the gold the head start they needed.
Oslo Sea Experience passes Kaholmane on its private fjord trips from Tjuvholmen.
The Norwegian version notes which facts were taken from each source: Kaholmane på norsk.