Text and photography by Sten Stockmann
Hitler’s plan for conquering Norway was simple. The heavy cruiser Blücher would sail into the Oslo harbor, turn its cannons against the royal palace, and Norway would surrender. The occupation forces would then take care of the rest. But things would not go fully as planned...
During the early morning hours of April 9th 1940 the mighty 206m long heavy cruiser Blücher enters the Oslo-fjord. The vessel is part of “Naval unit 5” led by contra-admiral Kummetz, and their task is to occupy the Norwegian capital. In addition to Blücher “Naval Unit 5” consists of the heavy cruiser Lützow, the light cruiser Emden, torpedo boats Albatross, Kondor and Möwe as well as eight vessels from the mine-sweeping flotilla. The vessels are transporting an occupation force of some 2000 infantry soldiers, 800 of which are aboard Blücher.

The Dröbak-straight is reached at 5am. In front, in the middle of the straight, lies the Norwegan fortress Oscarsborg. The commander of the fortress, Colonel Birger K. Eriksen has however already for some hours been awaiting the approaching German fleet, and soon the silhouette of the flagship Blücher is spotted. Knowing that his guns are outdated, and his crew inexperienced, Eriksen lets the ship come closers, and waits. The ships are already frightening close when he finally orders “Fire”.

With an enormous explosion two 280mm grenades hit the Blücher. The old cannons Aaron and Moses have spoken. The first shell hits above the bridge directly in the artillery command station killing the artillery commander and everyone nearby. The second one hits the hangar, where aircraft fuel and ammunition for the infantry soldiers have

been stored, starting a fierce fire. At the same time the Kopak and Husvik-batteries open fire with their 150 and 57mm guns. Heinrich Woldag, the commander of the Blücher orders “Fire Free” and the heavy and light AA guns open fire, but do not know where to shoot. Lacking targets the heavy guns remain silent. A few minutes later there is a second explosion as two torpedo’s hit the Blüchers side. These shots from the Norwegian underwater torpedo tubes are the final nails in Blüchers coffin. The vessel drifts unable to maneuver rapidly taking in water and a fierce fire burns midship. To prevent hitting a reef and hoping to still be able to start the engines Commander Woldag orders the anchor to be dropped. As the list of the sip increases it becomes evident that the ship is beyond rescue, and Woldag gives order to abandon ship. The seamen and soldiers jumping into the 3 degree Celsius water have 400m to swim to rescue, most without lifejackets. At 7.32 am it is over. The Blücher turns around and sinks, taking some 1500 men into the depths. 1023 are rescued.

The Oscarsborg’s big 280mm guns where bought from Krupp in 1892. During the transportation to the fortress one of these giant guns fell into the sea, and was named “Moses”. Soon after, the other guns where named Aaron and Joshua. So quite ironically the pride of the Nazis, the brand new heavy cruiser Blücher was sunk by German guns, with Jewish names.

Blücher history and operation Werserübung

The heavy cruiser Blücher was built at Deutche Werke shipyard in Kiel, and put to sea in June 1939. The vessel was put into service Sept 20th 1939, and was according to the German naval command too inexperienced to participate in the “Operation Weserübung”. But the Führer was of different opinion.

The objective of the Weserübung was to occupy the major harbors of the Norwegian coast. The occupation forces where transported by six naval units, destined for Narvik, Trondheim, Bergen, Kristiansand, Oslo and Egersund. Paratroopers where to seize control over the major airfields. The key to success of Weserubung lay in the early capture of Oslo.

As a result of the Blücher sinking, Oslo was not captured for several hours after the planned invasion of the capital, allowing the Norwegian royal family, parliament and cabinet to escape. In addition Norway’s gold reserves were moved out of reach of the invaders and ultimately shipped to the Allies for Norway’s use during the war.
Blücher today

The Blucher lies in 92m depth in the Oslo-fjord and is due to prevailing conditions a very demanding dive. In addition to the depth the vessel is turned upside-down, and strong tides make diving possible only at specific times. The heavy traffic in the straight is another danger. The whole of Oslo’s sea-traffic goes through, both freight ships and passenger ship to England. VHF-radio and a skilled and experienced surface-crew is a must. Due to this the Blücher is only dived a few times a year. Previously dived by Norwegian, Swedish and Danish teams, we had the honor of being the first Finns on the wreck.

Diving the Blücher

The morning starts early with getting our RIB’s into the water and preparing gear. There are two pairs diving today, one Norwegian and us. We are utilizing three RIB’s. One from which we dive, another holds the decompression station and the third one is ready to meet any arriving freight-ship, or for transportation to shore in case of emergency. On land we have a transportable
recompression chamber waiting, just in case. The decompression station consists of 3 “hang bars” at 12, 9 and 6m depth. In addition there is surface-supplied oxygen for the Norwegians from one of the boats. For safety reasons we opt to carry all decompression gases with us throughout the dive.

It is a calm and clouded morning, ideal for gearing up. We sit and wait as the Norwegian pair makes their final preparations for the dive. Due to the narrow tide-window we will start our descent 3minutes after the Norwegians. After the last pre-dive check we are transported 30m from the decent line. The surface current is so strong, that after jumping into the water I only barely have time to flush my mask and turn my light on before we already are at the descent line. The water tastes of oil, which regardless of the attempts to empty the wreck, still floats to the surface. I give my buddy Timo an OK signal and we start descending. Due to the current we are unable to drop freely, instead we have to pull ourselves down the line for a start. Gradually the current disappears, and we can start our long free-fall towards the bottom, 92m below us.

We are breathing a mixture of 12% oxygen and 60% helium, which at the 90m dive depth will give us a narcosis level equivalent of 30m on air. At 70m the darkness closes around us, and soon we can distinguish the lights of the Norwegian team below us. After 5minutes we finally reach the bottom at 90m. The visibility is ok, but not so good as expected, maybe 10m. The seabed is full of ammunition

and boots. We are midships and follow the m ast of the Blücher which lies on the bottom and steer for the hangar. Unfortunately the aircraft can not be admired, as it was raised to the Stavanger aviation museum in 1994. We study the badly damaged midship, and move closer towards the bow. On the way back we admire the “Wackeltopfs”, the ball shaped AA-sighting towers. Twenty minutes pass all too fast, and it is time to return towards our line and start the ascent. For the decompression we are carrying 3 bottles, and the first gas-switch is done at 60m. From here on we make stops every 3m. I find the seconds display in the gauge mode of my Suunto quite nice to control ascent rate and time the stops.

A safety diver arrives to check that everything is well. He gets two big smiles and ok-signs in return. Decompression time passes fast rewinding and reflecting over the dive we did, and exchanging a few words using a notebook. Exactly 95 minutes after the start of our dive we slowly break the surface. During our dive the cloud-layer has broken, and the sun greets us warmly.

Dive Details

The dive was planned using Decoplanner with Gf 20/95 settings. We extended the 57m and 21m stops, and added gas break for the O2 stop. The final ascent was 1m/min to surface. The schedule was a bit aggressive, but with support and chamber nearby, we felt DCI is smaller risk than drifting in a shipping lane if we loose ascent line. That is also why we carried all gasses with us the whole dive. We had 2x15 back gas bottles, and 1x10 21/35, 7l o2 and 7l ean50 bottles. Descent to 90m took almost 5min, as the current slowed us down in the beginning. Overall it was a great dive & everything went as planned!
Blücher- Technical Details
Vessel type Heavy Cruiser (Schwere Kreuzer)
Laid down Deutsche Werke, Kiel, 15. August1935
Launched 8. June 1937
Commissioned 20 September1939
Sister ships Admiral Hipper, Prinz Eugen, Seydlitz and Lützow
Tonnage 13900 t
Length 205,9 m
Width 21.3 m
Depth 5,8 m
Crew 1380 men
Weapons 8 x 20,3 cm, 12 x 10,5 cm, 12 x 3,7 cm, 28 x 2 cm, 12 torpedo tubes
Aircraft 3 pc Arado Ar 196, one catapult
Armament Deck 12-50 mm, side 70-80 mm, artillery 70-140mm
Propulsion 3 pc Blohm und Voss, together 132000 hp
Max. speed 32,5 knots
Range 6800 nm @ 19 knots
Location GPS: N 59 42.024 E 10 35.787