Battle

Main Battery rounds

One of the three 28 cm (11 in) main battery guns at Oscarsborg

While the main combat station for the Main Battery and the commander of Oscarsborg fortress was on the island Håøya north-west of South Kaholmen, due to the special circumstances in 1940, Oberst Eriksen took position in the backup station on the eastern flank of the main battery at South Kaholmen.

At 04:21 on 9 April, Eriksen gave the Main Battery guns the order to fire at the lead ship of the unknown flotilla forcing its way towards Oslo. Upon giving the command, Eriksen was questioned. He responded with his now famous response; \”Either I will be decorated or I will be court martialled. Fire!\” Two rounds from the 28 cm (11.0 in) Krupp guns Moses and Aron engaged the German cruiser Blücher at 1,800 m (2,000 yd) range. The two Norwegian guns had been loaded with live, 255 kg (562 lb) high-explosive shells; firing them \”in anger\” was a violation of the pre-war Norwegian rules of engagement which dictated warning shots be fired first, as had been the case at Oslofjord Fortress further down the fjord. Colonel Eriksen later explained his decision by alluding to the fact that the German naval force already had forced their way past the Oslofjord Fortress\’ forts and had received both warning shots and live rounds from these more outlying coastal fortifications. As the vessels had continued up the fjord toward the capital, Eriksen was of the opinion that he had the right to consider them enemy warships and to engage them as such.Oberst (Colonel) Birger Eriksen, the commander of Oscarsborg, 9 April 1940Map of Oslofjord and the fortress of Oscarsborg

The first 28 cm shell hit Blücher right in front of the aft mast, and set the midship area up to the fore mast on fire. The second 28 cm round hit the base of the forward 20.3 cm (8.0 in) gun turret shortly thereafter, throwing large parts of it into the fjord and igniting further fires on board. There was only time for the Main Battery to fire these two rounds, due to their slow reload time with only 30 untrained recruits manning them at the time. Only one gun crew of actual artillerymen was available, and two guns could only be made operational by splitting the real gunners between the two guns and using non-combatant privates to assist the gunners. The personnel pressed into service on the main guns included cooks woken up to man the Main Battery. There was no time to reload; there was not even time to fire the third gun, Josva, which was loaded but unmanned.

The reason for the significant effect of the two 28 cm rounds on Blücher was that the first round penetrated the side of the ship and exploded inside a magazine containing cans of oil, smoke dispensers, incendiary bombs, aircraft bombs for the cruiser\’s Arado Ar 196 reconnaissance floatplanes and depth charges. The bulkheads on that deck were blown out and the burning oil developed into an intense fire. The second 28 cm shell also knocked out the electricity central for the ship\’s main guns, rendering them unable to return fire.

Kopås and Husvik batteries

While fire raged aboard Blücher, the secondary Norwegian coastal batteries fired at her with guns ranging in calibre from the two small 57 mm (2.24 in) pieces at Husvik, intended to protect the fortress\’ missing mine barrier, to the three 15 cm (5.9 in) guns of the Kopås Battery on the eastern side of the fjord. The larger guns wrought havoc on board Blücher, while the 57 mm guns concentrated on the cruiser\’s superstructure and the anti-aircraft weapons, and were partially successful in suppressing the fire from her light artillery as Blücher slowly sailed past the fortress. The Husvik battery had to be abandoned when Blücher passed in front of it and fired her light AA guns directly down into the positions. Although the main building at the battery caught fire, the Norwegians suffered no casualties. In all, thirteen 15 cm rounds and around thirty 57 mm shells hit the German cruiser as it passed the guns of the fortress\’ secondary batteries. One of the 15 cm rounds from Kopås disabled Blücher\’s steering gear and forced the cruiser\’s crew to steer her using the engines to avoid running aground. Blücher\’s fire-fighting system was also knocked out by shell fragments from the two Norwegian batteries, making attempts to control the fires aboard the ship and rescue the many wounded much more difficult.

Identity of the intruders becomes known

As the now crippled Blücher passed the fortress guns, a sudden outburst of voices from the burning cruiser could be heard above the battle noises; Norwegian sources state that the crew broke into singing Deutschland, Deutschland über alles. Only at this point did it become clear to the men of the fortress whom they were fighting. Later, at 04:35, Oberst Eriksen received a message from the Norwegian minesweeper HNoMS Otra confirming that the intruding ships were German. The message had been sent to the naval base in Horten at 04:10, but the massive communications problems that severely hampered the efforts of the Norwegian military throughout the Norwegian Campaign had prevented it from reaching Oscarsborg in time.

The return fire from Blücher was ineffective, with the light artillery mostly pointing too high and the main batteries, 20.3 cm guns, unable to fire due to the damage caused by the second 28 cm round from Oscarsborg\’s Main Battery. The shelling lasted only for five to seven minutes. When the guns on both sides silenced, with all the \”passengers\” still under deck—\”there was a dead silence on board the whole ship, no movement whatsoever was identified\”.

Kommandørkaptein Anderssen launches the torpedoes

After passing the line of fire of the fortress\’ gun batteries, the cruiser was burning and severely damaged, but her captain still hoped he would be able to save his ship. At this point, however, Blücher entered the sights of Kommandørkaptein Anderssen as she slid past the torpedo battery at a range of only 500 m (550 yd). The torpedoes were 40-year-old Whitehead torpedo weapons of Austro-Hungarian manufacture. These torpedoes had been practice-launched well over 200 times before, but no one was certain if they would function or not. As Kommandørkaptein Anderssen pushed the firing mechanism button for the torpedoes, at approximately 04:30, the weapons turned out to work perfectly; first one and then another torpedo raced out of their underwater exit tunnels at 3 m (9.8 ft) below the surface toward the burning warship. As Anderssen had overestimated the speed of his target slightly, the first torpedo hit near Blücher\’s forward turret (nicknamed \”Anton\”), creating only inconsequential damage. The aim was corrected for the second torpedo launch and the torpedo struck Blücher amidships, hitting the same general area as the first 28 cm shell. This caused catastrophic damage to the cruiser and blew open many of her bulkheads, allowing water to flood her decks while she was burning furiously. The third torpedo launcher was left loaded in case more ships were to follow close behind Blücher. After firing, the two other tubes were reloaded and readied for the next target.

End of Blücher

Blücher on fire and sinking in Drøbak Sound

With all engines knocked out by the second torpedo hit, the cruiser anchored near the Askholmene islets just north and out of the arc of fire of the fort\’s guns to try to fight the ferocious fires raging throughout the vessel. Blücher\’s torpedoes were fired against land to avoid them exploding in the uncontrolled fires aboard. The crew\’s struggle ended when, at 05:30, fires reached a midship ammunition hold for the 10.5 cm (4.13 in) Flak guns, blowing a large gap in the ship\’s side. The magazine blast ruptured the bulkheads between the boiler rooms and tore open the cruiser\’s fuel bunkers, igniting further fires. By this point, Blücher was doomed.

At 06:22, Blücher sank bow first into the depths of the Oslofjord, first laying over on her port side, then turning upside-down and finally succumbing with her screws the last to disappear below the surface. After the ship had disappeared from the surface, large quantities of oil floated up and covered the close to two thousand sailors and soldiers fighting for their lives in the freezing water. The oil rapidly caught fire, killing hundreds more Germans.

Obergefreiter Günther Morgalla—who survived the sinking—later said that, swimming toward his shivering crew mates onshore, he heard someone defiantly singing the Deutschlandlied followed by \”Das kann doch einen Seemann nicht erschüttern.\” (\”That cannot shake a sailor\”). German survivors, with the sinking Blücher in the background

In all, 650–800 Germans died, and 550 of the approximately 1,400 wet and cold survivors of Blücher were captured by soldiers from Company no. 4 of the Norwegian Royal Guards under the command of Kaptein (Captain) A. J. T. Petersson. In total, some 1,200 of the survivors had made it ashore at Frogn near Drøbak. The guardsmen were supposed to take all the Germans prisoner, but mainly focused on caring for the many wounded and dying. Around 1,000 of the Germans, including Generalmajor Erwin Engelbrecht and Admiral Oskar Kummetz, were eventually moved to a nearby farm and placed under light guard. None of the prisoners were interrogated. By 18:30, the Norwegian soldiers withdrew from the area, abandoning the Germans. Engelbrecht and Kummetz then made their way to Oslo. The leading German officers reached Oslo at 22:00, moving into the Hotel Continental, though without most of the troops intended to occupy the capital.^[ Many of the German wounded were initially taken to Åsgården summer hotel in Åsgårdstrand for medical care, where Norwegian wounded had already been brought. The hotel was the temporary improvised location for the Royal Norwegian Navy Hospital, which had been evacuated from Horten at midnight on 8 April.