Oscarsborg Fortress

Why a fortress is there at all

Geography. Everything approaching Oslo by sea has to come through the Drøbak narrows, roughly 17 km of constricted water about a kilometre across, over a threshold only about 19 m deep. A gun position on an island in that gap commands the only door into the capital. The same sill that explains the fjord’s slow water exchange explains its fortress. The shape of the fjord.

9 April 1940, in the order it happened

Under the command of Colonel Birger Eriksen, the fortress fired its 28 cm Krupp guns at the incoming German force. Only two of the three fired — “Moses” and “Aron”; the third gun, “Josva”, did not. Then the underwater torpedo battery on Nordre Kaholmen, built between 1898 and 1901, put two torpedoes into Blücher. Those torpedoes were by then about forty years old. The ship went down in the sound. The Blücher, in detail.

What the sinking actually did

Not what the story usually says. The king, the government and about a hundred members of the Storting had already decided the night before to leave Oslo, on intelligence about approaching warships, and their train left Østbanen at around 07:23 to 07:30 — roughly an hour after Blücher went down at about 06:21. The sinking did not trigger the escape. What it did do was destroy the German flagship carrying the troops meant to seize the capital at dawn, delay the occupation of Oslo by hours, and give an evacuation that was already under way the room it needed.

Getting there

Not on a sightseeing cruise from central Oslo. The boats in this catalogue work the inner harbour and the near islands and turn around. Ruter’s B21 and B22 reach Drøbak, weekends in spring and autumn and daily in summer, which makes a day south possible if you check the day you are actually going. Drøbak and the narrows.

Frequently asked questions