The Nazi invasion of Norway in 1940 succeeded quickly and efficiently but only after a dramatic initial setback.

Needing to protect its vital supply of steel from Northern Sweden and also to secure submarine bases for the North Sea, Germany devised a plan to attack Norway at five different locations: Narvik, Trondheim, Bergen, Kristiansand/Arendal, and Oslo. This plan worked well and control of the whole country was achieved in a few days. Norway was not expecting an imminent invasion and thus had limited defences. 

Initially, however, the Germans suffered one disaster: their naval attack on Oslo was repulsed when the lead ship of their convoy, a top-of-the-line, modern heavy cruiser, was sunk by Norwegian guns. Today the Blücher still lies at the bottom of the Oslofjord some 25km short of its Oslo destination. 

German Convoy

The German plan to take Oslo involved a convoy of four ships from Swinemünde (the Blücher; the Emden, a light cruiser; the Lüzow, a heavy cruiser; the Möwe, a WW1 merchant raider, as well as two auxiliaries). In addition to the crews, transport vehicles and ammunition, there were also 170,000 foot soldiers on board. 

Under Rear Admiral Kummetz, the convoy departed on April 8. As it steamed through the Kattegat sea between Denmark and Sweden, it encountered the British sub Triton, which fired off some torpedoes. The convoy managed to avoid them and proceeded north. Nevertheless, the British informed the Norwegians of this German convoy, and an order was sent out to set up a mine barrage across the entrance to Oslofjord. 

On schedule, the convoy reached the entrance to Oslofjord just after nightfall at 23:30—well before the mine barrage was set. The plan was to cover the 100km to Oslo in the dark. Although the fog was thickening, some of the German boats were spotted by a Norwegian patrol boat, Pol III, which managed to radio an alarm. The two Norwegian batteries guarding the fjord’s wide entrance both reacted: Rauoy caught some of the convoy in its searchlight and fired off two warning shots; Bolearne managed to fire one warning shot. Doubts about the identity of the convoy—despite the warning from Triton--led to this indecisive Norwegian action.

As the convoy steamed north at 12 knots, the Norwegian authorities ordered all lighthouses and navigation lights extinguished.  It was now dark and foggy—perfect cover for the German invaders.  The convoy stopped at Horten, 24k on, in order to drop off 150 land troops and to join up with R-boats. The Norwegian military base at Horten was aware of the ships, but like the forts at Rauoy and Bolearne, it didn’t react decisively as there was still doubt about the identity of the ships.

The convoy set off again at 02:30, led by the now battle-ready Blücher. It was followed by the Lutzow, the Emden,  the Möwe, each 600m apart, and the R-boats. Soon they were approaching the main defences at Oscarsborg, where the fiord narrowed considerably. Because of the early encounter at the mouth of the fiord, the Norwegian command had finally decided that the convoy would have to be attacked if it tried to pass Oscarsborg. 

The Oscarsborg fort was not in good shape despite repeated requests over the years from its commander to modernize. It had just three 28cm Krupp guns. Supporting guns were across the narrows at Kopas (three 15cm guns), Husvik (two 57mm guns) and Nesset (three 57mm guns). At this time only one third of the staff was on duty at Oscarborg, meaning that only two of the three guns could be used. The forts at Husvik and Nesset were also compromised as new crews had arrived only a week before. 

The Battle

Kummetz, the convoy leader on the Blücher, decided to enter the narrows at 03:30, just before first light. Despite the fog and darkness, the Blücher was soon seen and reported by two Norwegian auxiliaries at Filtvet, near the start of the narrows. As it approached the guns of Oscarsborg at 04:15, the convoy was suddenly caught in a powerful searchlight from Kopas. Oscarsburg was informed, and four minutes later the order to fire was given. The Battle of Drobak Narrows had begun. 

The first 28cm shell, set at the range of 1400m, hit the lower part of the Blücher’s control tower and destroyed the main flak platform. A second shell, a few seconds later, hit the Blücher’s port side just aft of the funnel. It wrecked the aircraft hangar, which contained two planes, and killed many of the foot soldiers assembled below deck. Smoke filled the boiler and engine rooms. The captain, unable to locate the source of the gunfire, asked for full power, but the engine room could not oblige as not all the boilers were in use. 

The Blücher was now attacked on its other side by the Kopas and Husvik guns. Kopas fired twenty-three 15cm shells and Husvik thirty-six 57mm shells. Almost all hit the Blücher, starting many fires. The Kopas guns were so close that the shells penetrated the Blücher’s superstructure. The fires soon reached the fuel, ammunition and explosives on board. Loss of electricity and steering problems followed. Water now poured into the ship, and when the pumps stopped working, the ship began to list. Then, after the turbines stalled and power was lost, the Blücher became unmanoeuvrable. Kummetz decided to drop anchor in order to avoid running ashore. 

Since the burning Blücher now sat stationary in the middle of the channel, the Norwegian guns now turned on the second ship, the Lutzow. After several minor hits, it retreated. The next boat behind the Lutzow, the Emden, was not hit at all. The rest of the German convoy had disappeared from Kopas by 04:40. 

The Blücher Sinks

Meanwhile the crew of the Blücher, as well as the gunners and the boiler crew, were trying to stem the fires. As the pumps had failed, movement on board was severely limited. The Blücher began listing badly. Attempts were made to get the wounded ashore, but the main rescue boat hit a rock. Only a few men were actually rescued by boat. The only other way to safety was a 15-minute swim in icy waters. 

By 05:00 the fire on the Blücher was getting out of hand. The crew had to deal with smoke and rising water. At 05:30 a magazine of firearms exploded and jolted the whole ship. When the list worsened even more, plans were made to abandon ship. Code lists and other secret documents were hastily destroyed or thrown overboard. Few of the foot soldiers below deck could swim, and many of the life jackets had been burnt. When the list reached 45 degrees, the order to abandon ship was given.

Kummetz himself jumped into the water without a life jacket. He was halfway to the shore when the Blücher went down at 06:25. He made it to shore—a difficult swim as the leaking fuel on the water’s surface had caught fire. Many of those who swam for safety were killed by this fire. Estimated German losses vary between 600 and 1,000.

Aftermath  

After retreating, the remainder of the convoy landed troops on the east side of the fjord. They took the Oscarsborg fortress by 09:00 the next day and then moved on to attack Oslo. Meanwhile airborne troops had taken over the Oslo airport at Fornebu Airport and by 14:00 on April 10, the Norwegian capital was under German control.

Today, the Blücher still rests at the bottom of the Oslofjord at the Drobak Narrows. It took a lot of oil to its 60m grave and has leaked its fuel over the years. In 1994, after 54 years, divers tried to stop the leaking. They removed some 1,000 tons of oil, but experts still believe more is down there.  

I am indebted to Geirr H. Haarr’s The German Invasion of Norway, April 1940 for much of the information in this article.