Battle of Drøbak Sound

Infobox Military Conflict
conflict=Battle of Drøbak Sound


caption="Blücher" sinking in the Oslofjord.
partof=the Norwegian Campaign of World War II
date=9 April 1940
place=Drøbak Sound, Norway
result=Decisive Norwegian victory
combatant1=Norway
combatant2=Nazi Germany
commander1=Birger Eriksen
commander2=Oskar Kummetz
strength1=Oscarsborg Fortress:
Main Battery:
3 × 28 cm coastal guns
4 × anti-aircraft machine gunsFjeld 1999: 190]
Kopås Battery:
3 × 15 cm coastal guns
Husvik Battery:
2 × 57 mm mine barrier protection guns
Torpedo Battery:
3 × doubleStangeland&Valebrokk 2001: 260] 45 cm land based underwater torpedo launch tunnelsFjeld 1999: 160]
Seiersten Battery:
2 × Bofors 40 mm L/60
anti-aircraft guns
3 × Colt M/29 7,92 mm anti-aircraft machine guns
Håøya Battery:
(part of nearby
Tønsberg Fortifications)
4 × Colt M/29 7,92 mm anti-aircraft machine guns
Infantry support:
One company of the
Norwegian Royal Guards
Total crew:
45 officers
293 NCOs and men,
69 officers and men of the Norwegian Royal GuardsHauge 1995: 42]
strength2=1 × heavy cruiser
1 × pocket battleship
1 × light cruiser
3 × torpedo boats
8 × minesweepers
casualties1=No casualties, although most buildings above ground at the Main Battery were burnt to the ground. [Ribsskog 1998: 55]
casualties2=1 heavy cruiser sunk
1 pocket battleship damaged
650-800 deadRibsskog 1998: 53]
ca. 50 wounded
550 temporarily taken prisoner
casualties3=Civilian casualties:
Three houses destroyed and two women killed by stray German shells in nearby Drøbak. [Fjeld 1999: 189]
Cargo cutter "Sørland" sunk by German minesweepers with the loss of two crewmen.Warsailors.com: [http://www.warsailors.com/homefleet/shipss2.html#Sy M/K "Sørland"] en icon] Skovheim Shipwreck website: [http://www.skovheim.org/located/akershus/sorland/sorland.htm "Sørland"] no icon&en icon]

The Battle of Drøbak Sound took place in the in northernmost part of the Oslofjord on 9 April 1940, on the first day of the German invasion of Norway. It was the start of the war in Western Europe — and an end to the "Phoney War".

Oscarsborg Fortress engaged a German fleet sailing up the Oslofjord with the objective of seizing the Norwegian capital and capturing Haakon VII, the Norwegian king, and his government. At the time of the battle, the aging fortress' Main Battery of guns was over forty years old and the installation had been relegated to training coastal artillery servicemen, leading the Germans to disregard the fortress' defensive value. Furthermore, the most powerful weapon of the fortress was a torpedo battery, which no one but the Norwegian military knew about.Kongsberg Defence Association: [http://www.kongsberg.net/forsvarsforeningen/frame.asp?Id=48592 Guided tour of Oscarsborg Fortress] no icon]

In the end, the fortress' armament worked flawlessly. By sinking the lead ship of the German armada headed for Oslo Oscarsborg Fortress saved the Norwegian king and government from being taken captive in the first hours of the invasion.

Before the Battle

As the political situation was chaotic, the aging 65 year commander, oberst (Colonel) Birger Eriksen had not received any clear orders and had received no notice as to whether the approaching warships were German or Allies. He was well aware that Norway was officially neutral, but that the government was inclined to side with the British in case of direct Norwegian involvement in the war. As he was about to give orders to fire, Eriksen said: "Either I will be decorated or I will be court-martialed. Fire." [Lofoten War Museum: [http://www.lofotenkrigmus.no/april2.htm 9 APRIL] no icon]

Apart from the officers and NCOs, almost all soldiers manning the fortress were fresh recruits, having only been conscripted seven days before, on 2 April. Because of the influx of four hundred and fifty fresh recruits, the fortress' naval mines were not deployed on 9 April. Part of the recruits' training was to lay the mine barrier, a process planned for a few days later.

The torpedo battery

The commander of the torpedo battery at Oscarsborg had at the time of the battle been on sick leave since March 1940. Due to this the retired kommandørkaptein (Commander Senior Grade) Andreas Anderssen, who lived in nearby Drøbak, had been assigned as temporary commander for the battery. As an unidentified flotilla started forcing its way past the outer fortifications in the south of the Oslofjord, late at night on 8 April, oberst Eriksen called Anderssen in and had him come down to the fortress. Kommandørkaptein Anderssen donned his old uniform and was transported by boat over the fjord to the torpedo battery. [Hansen 2005: 49] Andersen would show himself worthy of the important task of leading the fortress' most lethal weapon system; having first served at the torpedo battery in 1909 he knew the ageing weapons intimately. [Aftenposten Newspaper: [http://www.aftenposten.no/fakta/verdenskrig/article449062.ece?service=print Fra time til time] no icon] When Anderssen had been called back into duty a month previously he had been a pensioner for 13 years, having originally retired from his post as commander of the torpedo battery in 1927. [Hansen 2005: 48] The battery has three torpedo tunnels which could fire six torpedoes without reloading and a total of nine torpedoes were stored and ready for use.

The Battle

The Main Battery rounds

At 0421hrs 9 April 1940 Oberst Eriksen gave the Main Battery guns the order to fire at the lead ship of the unknown flotilla forcing its way towards Oslo. Two rounds from the 28 cm Krupp guns "Moses" and "Aron" (Aaron) engaged the 14,000 tonne German cruiser "Blücher" at 1,800 metres range. The two Norwegian guns had been loaded with live, 255 kg brisant shells,Hauge 1995: 35] 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. [Aftenposten Newspaper: [http://www.aftenposten.no/fakta/verdenskrig/article449062.ece The invasion from hour to hour] no icon] [Robert's website: [http://hem.fyristorg.com/robertm/norge/timetable.html The invasion hour by hour] en icon] 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 towards the capital, Eriksen was of the opinion that he had the right to consider them enemy warships and to engage them as such.The first 28 cm shell hit the "Blücher" right in front of the aft mast,Ribsskog 1998: 50] and set the midship area up to the fore mast on fire. [Ribsskog 1998: 50-51] . The second 28 cm round hit the base of the fore 20.3 cm gun turret shortly thereafter, throwing large parts of it into the fjord and igniting further fires on board.Ribsskog 1998: 51] 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 even was no time to fire the third gun, "Josva" (Joshua), which was loaded, but unmanned.

The reason for the significant effect of the two 28 cm rounds on the "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, airplane bombs for the cruiser's Arado Ar 196 reconnaissance seaplanes 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.The return fire from "Blücher" was ineffective, with the light artillery mostly pointing too high and the main batteries, 20.3 cm guns, could not fire due the damage caused by the second 28 cm round from Oscarsborg's Main Battery.

The Kopås and Husvik batteries

While fire raged aboard the "Blücher", the secondary Norwegian coastal batteries pelted her with guns ranging in caliber from the two small 57 mm pieces at Husvik, intended to protect the fortress' missing naval mine barrier, to the three 15 cm guns of the Kopås Battery on the eastern side of the fjord. The larger guns wrought havoc on board the cruiser while the 57 mm guns concentrated on the cruiser's superstructure and the anti-aircraft weapons,Fjeld2 1999:36] and were partially successful in suppressing the fire from her light artillery as the "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. All 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 the "Blücher"'s steering system and forced the cruiser's crew to steer her using the engines and propeller to avoid running aground. The fire fighting system on the "Blücher" 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.

The 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, the crew and passengers breaking into singing "Deutschland, Deutschland über alles".Hauge 1995: 36] Tamelander&Zetterling 2001: 87] Berg 1997: 13] Only at this point did it become clear to the men of the fortress whom they were fighting.Berg 1997: 12-13] [Ribsskog 1998:45-50] [Grimnes 1990: 7-8] Later, at 0435hrs, Col. 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 0410hrs, 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. [Berg 1997: 10]

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, the "Blücher" entered the sights of Kommandørkaptein Anderssen as she slid past the torpedo battery at a range of only 500 meters. The torpedoes the retired officer was aiming at the cruiser were 40-year-old Whitehead 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 the weapons turned out to work perfectly, first one and then another torpedo raced out of their underwater exit tunnels at three meters below the surface towards the burning warship. As Anderssen had overestimated the speed of his target slightly the first torpedo hit near the "Blücher"'s forward ("Anton") turret, creating only inconsequential damage. With the second torpedo launch the aim was corrected and the torpedo struck the "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 the "Blücher"

With all engines knocked out by the second torpedo hit, the cruiser anchored near the Askholmene islets to try and fight the ferocious fires raging throughout the vessel. The "Blücher"'s torpedoes were fired against land to avoid them exploding in the uncontrolled fires aboard.Hauge 1995: 38] The crew's struggle ended when, at 0530hrs, fires reached a midship ammunition hold for the 10.5 cm Flak guns, blowing a huge gap in the ship's side.Williamson 2003: 33-34] [Tamelander&Zetterling 2001: 88] The magazine blast ruptured the bulkheads between the boiler rooms and tore open the cruiser's fuel bunkers; igniting further fires. By this point the "Blücher" was doomed.

At 0622hrs the "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 further hundreds of Germans.

All in all, some 650-800 Germans died, and some 550 of the around 1,400 wet and cold survivors of the "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 and the guardsmen were supposed to take all these as prisoners, but instead focused on tending for the many wounded and dying. [Hansen 2005: 71] By doing this the Norwegians neglected their original orders and allowed for the German top officers, chief amongst whom was Major General Erwin Engelbrecht, to slip away to the nearest road and capture a Norwegian truck on gunpoint. The German leading officers reached the Hotel Continental in Oslo only two hours later than planned, though without the troops intended to occupy the Norwegian capital. [Hansen 2005: 72] 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. [Sivertsen 2001: 78]

The remaining ships turn around

By the time the "Blücher" sank, the remaining naval force destined for Oslo had long since turned around and retreated back down the fjord. Unaware of the torpedo battery, the commander of the "Lützow" assumed the flagship had hit mines and at 0440hrs the decision was made to turn back and land the invasion forces out of range of Oscarsborg. The planned coup against Oslo to force the surrender of the Norwegian government was replaced by a land advance up the Oslofjord. [Grimnes 1990: 14]

As the force made good its escape the fortress managed to damage the "Lützow", the 15 cm guns of the Kopås battery scoring three hits and knocking out the ship's aft ("Bruno") 28 cm gun turret. Kopås kept firing at the retreating ships until they disappeared in the mist at a range of around 3,000 meters. After pulling out of range of the fortress guns the "Lützow" employed her remaining "Anton" turret to bombard the defenders from a range of 9-10 kilometers down the fjord.

During the battle another burning ship was spotted in the distance from Oscarsborg, leading the Norwegian defenders to believe they had sunk one more German warship in addition to "Blücher". For some time after the battle the belief was that Oscarsborg had sunk the artillery training ship "Brummer". The reality, however, was that the burning ship was the 107 ton Norwegian cargo cutter "Sørland" that had stumbled into the battle while on her way from Moss to Oslo with a cargo of paper. As the small ship had mistaken the events as a military exercise she had kept going until fired upon and set ablaze by the German minesweepers "R-18" and "R-19". The "Sørland" sank with two of her six man crew near the village of Skiphelle in Drøbak, as the first civilian Norwegian ship lost during the invasion. The German "Brummer" was indeed lost in connection with the invasion, but only when she was on her way back to Germany on 14 April, when she was torpedoed by the Royal Navy submarine HMS "Sterlet" and sank the next day. [German-navy.de: [http://german-navy.de/kriegsmarine/ships/training/brummer/history.html "Brummer"] en icon]

Luftwaffe bombing

The fortress was subjected to heavy Luftwaffe bombing later on the same day, to which the fortress could only reply with two Bofors 40 mm L/60 AA guns and three outdated Colt M/29 7,92 mm AA machine guns at Seiersten Battery, as well as another four Colt M/29 7,92 mm AA machine guns at Håøya Battery, [Grimnes 1990: 15] but again without Norwegian casualties. Initially four machine guns on the roof of the Main Battery also returned fire, but these had to be abandoned early on in the bombing.

One of the two 40 mm anti-aircraft guns became unserviceable after only 22 rounds; the other gun kept firing until 1200hrs, but to little effect. After a break in the attacks from 1200 to 1330hrs, during which time "Lützow" bombarded the Main Island, the Luftwaffe bombers returned at 1330hrs and soon strafed the remaining Norwegian AA gun, forcing the crew to seek shelter in the nearby forest at around 1400hrs. In all, the fortress was subjected to close to nine hours of air attack, during which time around 500 bombs, ranging from 50 to 200 kgs in size, were dropped on Oscarsborg.Fjeld 1999: 191]

urrender

Although the naval attack on Oslo had been thwarted by the actions of Oscarsborg, the city was seized by forces that were airlifted in to Fornebu Airport. In light of the capture of the capital, and with news of German landings at the village of Son south of Drøbak, Colonel Eriksen decided that further fighting without adequate infantry support was in vain. The fortress was surrendered intact on the morning of 10 April.

Aftermath

The effect of halting the German fleet was huge. On board the "Blücher" were troops specially designated to capture the King, the Norwegian cabinet, the Storting (Norwegian Parliament) and the national gold reserve. The delay made it possible for all these to escape from Oslo. Later in the day of 9 April, the Storting was able to convene at Elverum and give the cabinet a wide authorization to govern until a Storting could again assemble. Thus, the Norwegian government was able to continue the defence of Norway until it had evacuate to exile in the UK on 7 June, with the Norwegian Army putting down their arms on 10 June.

Notes

Literature

*, Oslo 1997 ISBN 82-993545-2-8 no icon
* no icon
* no icon
* no icon
(to be quoted as Fjeld2 1999)
* no icon
* no icon
* no icon
* no icon
* no icon
* no icon
* no icon
* Williamson, Gordon: "German Heavy Cruisers 1939-45", Osprey Publishing Ltd., Oxford 2003 ISBN 1-84176-502-3 en icon

External links

* [http://www.nasjonalefestningsverk.no/oscarsborg Oscarsborg fortress official website] no icon
* [http://www.oscarsborg.no Website on the fortress] no icon
* [http://www.oscarsborgmuseum.no/historie.htm Oscarsborg Museum - history of the fortress] no icon&en icon
* [http://www.mil.no/felles/ofm/start/Historie/ Norwegian Defence Force website page about the fortress] no icon
* [http://www.aftenposten.no/fakta/verdenskrig/article449062.ece 50 year anniversary Aftenposten newspaper article on the invasion of Norway] no icon
* [http://www.admiral-hipper-class.dk/bluecher/miscellaneous/oscarsborg_bluecher_wreck_site_today/oscarsborg_bluecher_wreck_site_today.html Admiral-hipper-class.dk on Oscarsborg] en icon