Unternehmen Weserübung was the code-name given to the German assault on the countries of Denmark and Norway. Sweden would ultimately play a pivotal role in the conflict as would Finland whose war with the Soviet Union on the 30th November 1939 would have a direct influence over the decision of the German High Command to prosecute this campaign and would draw the Russians into an ideological power struggle with Nazi Germany culminating in Operation Barbarossa, the invasion of the Soviet Union by the Axis powers. Britain and France would become directly involved in this ‘Scandinavian War’ the victor of which would control the mineral rich resources of the region.
At 04:15 (05:15 ‘Weser time’ or German time) on the 9th April 1940 (Wesertag; “Weser Day”), Germany invaded Denmark and Norway. The political motives behind this offensive were said to be a preventative tactic against a Franco-British occupation of Norway which had been openly discussed by the Governments of both countries.
The German Ambassadors to both Norway and Denmark informed the administrations of each nation that the Wehrmacht had come to ‘protect’ their National neutrality against Franco-British aggression.
Political and military background of the operation
During the spring of 1939, the British Admiralty began to consider the possibility of using Scandinavia as a potential theatre of war with Germany. A continental land battle had been ruled out by the British government due to the conceivable repetition of the First World War. Therefore a blockade strategy was considered in order to weaken Germany economically, using the vastly superior resources of the Royal Navy to deny Germany iron ore from the Swedish mining district upon which it was heavily dependent. Much of this ore was shipped through the northern Norwegian port of Narvik during the winter months, therefore control of the Norwegian coast was considered vital in the enforcement of a blockade against Germany.
Großadmiral Erich Raeder, the chief of the German Kriegsmarine became concerned that the British occupation of Norway posed an unacceptable risk to Nazi Germany. In October 1939, he discussed his concerns with Adolf Hitler, further arguing that should Germany possess Norwegian Naval bases before the British, they could threaten merchant shipping to the United Kingdom through a concerted submarine campaign thereby severely disrupting vital British trade. Hitler was not interested, having just issued a directive stating that the main military effort would be a land offensive through the Low Countries with an attack on France being the ultimate objective of the German armed forces.
Operation Wilfred, the proposed anti-ship mining of Norwegian waters, was suggested by Winston Churchill, then a new member of the British War Cabinet toward the end of November. The enterprise was designed to force Swedish and Norwegian ore transports through the open waters of the North Sea where they would be intercepted by the Royal Navy thus denying Germany vital supplies. It was intended that such a move would provoke a German response in Norway. Any German incursion into neutral Norway would provoke the Allies into implementing Plan R4 and occupy Norway themselves.
Though later implemented, the plan was initially rejected by Neville Chamberlain and Lord Halifax, due to a fear of an adverse reaction amongst the neutral nations, in particular the United States. Churchill proposed the plan once again after the Soviet Union had attacked Finland on the 30th November 1939. The mining scheme was denied once again.
In December shortly after the invasion of Finland by the Soviet Union, the United Kingdom and France began serious planning for sending aid to Finland. The plan called for a force to land at Narvik in northern Norway, the main port for Swedish iron ore exports, and to take control of the Malmbanan railway line from Narvik to Luleå in Sweden on the shore of the Gulf of Bothnia. Conveniently, this plan also would allow the Allied forces to occupy the Swedish iron ore mining district. The plan received the support of both Chamberlain and Halifax. They were counting on the cooperation of Norway, which would alleviate some of the legal issues; however, strongly negative reactions in both countries curtailed its implementation. Planning for the expedition continued, but the justification for it was removed when Finland sued for peace in March 1940.
When the Soviet Union attacked Finland on the 30th November 1939, the Allies (principally the British and the French) found themselves allied to the Swedish and the Norwegians in support of Finland against the Soviet Union which was still subject to the Molotov-Ribbentrop pact and thus an ally of Nazi Germany.
In response to the Soviet attack, the Norwegians mobilized 9,500 troops of the 6th Division to Finnmark and Troms. The mobilization had been largely completed by the beginning of 1940. Curiously, part of the 6th division remained in the Eastern regions of Finnmark after the German attack in the event that the Soviets should strike.
During the Winter War both Norway and Sweden exercised ‘non- belligerence’ in direct contravention of their neutrality by sending troops, weapons and supplies to Finland. Sweden sent money, food, 135,000 rifles, large quantities of ammunition, 330 artillery pieces, approximately 8,700 volunteers and the Swedish Voluntary Air Force – Flygflottilj19, which consisted of 12 Gloster Gladiator fighters and 5 Hawker Hart Bombers all crewed by Swedish volunteers.
Norway sent a shipment of 12 Ehrhardt 7.5cm Model 1901 artillery pieces and 12,000 shells. In addition the Norwegian Government allowed the British to use Norwegian territory to transit aircraft and other weaponry to Finland.
Whilst the Allies were genuinely sympathetic to Finland, these events also presented them with an opportunity to send troop support to Narvik to occupy the iron ore fields in Sweden and ports in Norway.
The plan, prepared by British General Edmund Ironside, included two divisions landing at Narvik, five battalions in mid-Norway and a further two divisions at Trondheim. The French were keen to push for this action to divert German attention from France.
The landings in Norway by the British caused the Germans concern. The Molotov-Ribbentrop Pact had placed Finland within the Soviet sphere of interest, and the Germans therefore claimed neutrality in the conflict. This policy caused a rise in anti-German sentiment throughout Scandinavia, since it was commonly believed that the Germans were allied with the Soviets. The German high command became concerned that Norway and Sweden would allow Allied troops to cross their territory to aid Finland.
The proposed Allied deployments of troops never occurred. Protests from both Norway and Sweden, due to the contravention of their neutrality, denied the Allies access to Finland. With the Moscow Peace Treaty on 12 March 1940, the Finland-related Allied plans were dropped. The abandonment of the planned landings put immense French pressure on Neville Chamberlain’s British government, and eventually led to the Allied mining of the Norwegian coast on 8 April.
While Germany and Sweden pressured Finland to accept peace on unfavorable conditions, Britain and France had the opposite objective. Different plans and figures were presented for the Finns. At first, both France and Britain promised to send 20,000 men who were to arrive by the end of February. By the end of that month, Finland’s Commander-in-Chief, Field Marshal Mannerheim, was pessimistic about the military situation. Therefore, on 29 February the government decided to start peace negotiations. That same day, the Soviets commenced an attack against Viipuri.
When France and Britain realized that Finland was considering a peace treaty, they gave a new offer of 50,000 troops, if Finland asked for help before 12 March. Through Soviet agents in the French and British governments, indications of Franco-British plans reached Stalin, and may have contributed heavily to his decision negotiate an armistice with the Finnish government on March 13th 1940.
The Economic Importance of Swedish Iron Ore during WWII
Swedish iron ore was an important economic factor in the European Theatre of World War II. Both the Allies and the Third Reich were keen on the control of the mining district in northernmost Sweden, surrounding the mining towns of Gällivare and Kiruna. The importance of this issue increased after other sources were cut off from Germany by the British sea blockade during the Battle of the Atlantic. Both the planned Anglo-French support of Finland in the Winter War, and the following German occupation of Denmark and Norway, were to a large extent motivated by the wish to deny their respective enemies iron critical for wartime production of steel.
Winston Churchill, then First Lord of the Admiralty was particularly concerned about Swedish exports of iron ore to Germany, and pushed for the British government to take military action to end the trade. From the beginning of the war Churchill tried to persuade his cabinet colleagues to send a British fleet into the Baltic Sea to stop shipping reaching Germany from the two Swedish iron ore ports, Luleå and Oxelösund. The project was called Project Catherine and was planned by Admiral of the Fleet William Boyle, 12th Earl of Cork. However, events overtook this project and it was canceled. Later, when the Baltic ports froze over and the Germans began shipping the iron ore from the Norwegian port of Narvik, Churchill pushed for the Royal Navy to mine the west coast of Norway to prevent the Germans travelling inside neutral territorial waters to escape Allied Contraband Control measures.
At the outbreak of World War II on 3rd September 1939, Britain and France enacted a naval blockade of Germany similar to the blockade initiated with great success during the First World War. Germany, a country lacking in natural resources and heavily reliant on large scale imports of a wide range of goods was heavily reliant on mercantile trade. Perhaps the material Germany needed above all others was iron ore, a steady supply of which was imperative in the creation of steel to sustain her war effort and general economy.
In 1938, Germany imported 22 million tons of iron ore from various foreign sources. She was able to produce 10 tons of her own iron ore each year. This was however of low-grade quality and needed to be mixed with superior grade material from countries such as Sweden, which supplied Germany 9 million tons annually. 7 million tons of the Swedish ore came from Kiruna and Gällivare in Lapland and 2 million from the central Swedish ore field’s north-west of Stockholm.
With the outbreak of war, Germany lost approximately 9 million tons of iron ore per annum. She still had access to 3 million tons from Norway and Luxembourg; in addition 10 million tons per year were available from Lorraine in France. Supplies from Morocco and Spain were no longer accessible due to the British presence in Gibraltar, which meant that the remaining supplies available from neutral Scandinavia became crucial.
Grand Admiral Raeder, head of the German navy, declared that it would be “utterly impossible to make war should the navy not be able to secure the supplies of iron-ore from Sweden”.
Britain also relied heavily on large quantities of imported iron ore. The Royal Navy routinely stopped ships of all nations for inspections to ensure that they were not delivering important supplies to the enemy. Germany considered the Franco-British blockade to be illegal and therefore embarked upon a system of unrestricted submarine warfare. All vessels whether enemy or neutral could be attacked. This policy continued for the first nine months of the war resulting in a considerable loss of life.
The French and the British Fleets exercised a policy of leniency towards neutral vessels in an effort not to alienate them. The Allies were keenly aware that to not do so could result in sympathy for the German people and that many neutral mariners relied on Germany for trade.
Iron ore routes
There were two main routes by which iron ore was shipped to Germany from Sweden.
The Eastern Route
From May to November, iron ore from the Northern region was shipped from the port of Luleå down the Gulf of Bothnia to the German north Baltic ports at Lubeck, Swinemunde, and Stettin. From December to April, the Gulf of Bothnia froze over, severely restricting supplies, and although an alternate port was available at Oxelösund, south of Stockholm for the transport of iron ore from the mines in Bergslagen, this facility was unable supply the full amount required by Germany, and in any case froze over itself from January to March each year. Luleå remained outside the reach of Royal Navy’s patrols but it was estimated that when Luleå and the Baltic ports of Oxelösund and Gävle were open it could only supply around 8million tons, or less than half of the pre-war imports.
This meant that during the early winter months of the war, Germany had no choice than to transport the majority of its ore along the much further route down Norway’s heavily indented Western coast from Narvik
The Western Route (“Norwegian Corridor”, Western Leads or Skjaergaard)
The port of Narvik, high above the Arctic Circle was open for iron ore shipments all year round. But the stormy Atlantic coast of Norway also provided another extremely useful geological feature for Germany in her attempts to continue shipping the ore and beating the allied blockade.
Immediately offshore from Norway’s western coast lies the Skjaergaard (Skjærgård), a continuous chain of some 50,000 glacially formed skerries (small uninhabited islands) sea stacks and rocks running parallel to the shore. A partially hidden sea lane (which Churchill called the Norwegian Corridor) exists in the area between this rocky fringe and the coastal landmass proper. Inside this protected channel it is possible to navigate the entire 1,600 km length of the Norwegian coast from North Cape to Stavanger. Such coastlines, sometimes known as Leads — a rough English translation for the common Norwegian nautical term Ledene (shipping lane) are common around Scandinavia — Skjaergaard also exist along the Swedish and Finnish Baltic coasts and off Greenland.
The Germans made great use of the Norwegian Corridor to avoid the attention of the vigilant Royal Navy and RAF. In the winter of 1939–1940 a steady stream of their specially-constructed iron ore vessels made the long trip south from Narvik, sometimes within the three mile curtilage of neutral Norwegian territorial waters, sometimes just outside if the way appeared hazardous or the sea particularly turbulent. At the southernmost point the iron ore captains had to make a choice:
- Follow the Skjaergaard around the coasts of Norway and Sweden, down through the Kattgat and finally into the north German Baltic ports of Lubeck and Stettin. This route was safer because it brought them much closer to the protection of the German naval patrols and Luftwaffe air cover but involved hauling the very bulky and heavy iron ore the long way overland to the industrial centres on the overburdened German railway system.
- Leave the safety of the Skjaergaard and make a dash south across the Skagerrak, (the sea channel north of the Danish Jutland peninsula) and dash down the west coast of Denmark to Hamburg and Bremen. This was the preferred route because it allowed the ore to be taken straight along the efficient inland waterways to the industrial heartlands of the Ruhr and the Rhineland where it could be processed. It was much more hazardous, putting the ships and their cargo at the mercy of allied submarines and patrolling destroyers of the Contraband Control. A number of German ships were sunk in this area.
British attempts to disrupt German-Swedish trade
From the beginning of the war, Winston Churchill expended considerable energies trying to persuade his colleagues in the British government to take action to stop the iron ore traffic. On 16 December 1939 he issued a memo to the cabinet:
‘It must be understood that an adequate supply of Swedish iron ore is vital to Germany…the effectual stoppage of the Norwegian ore supplies to Germany ranks as a major offensive operation of the war. No other measure is open to us for many months to come which gives so good a chance of abridging the waste and destruction of the conflict, or of perhaps preventing the vast slaughters which will attend the grapple of the main armies. The ore from Luleå (in the Baltic) is already stopped by the winter ice, which must not be broken by the Soviet ice-breaker, should the attempt be made. The ore from Narvik must be stopped by laying successively a series of small minefields in Norwegian territorial waters at the two or three suitable points on the coast, which will force the ships carrying ore to Germany to quit territorial waters and come on to the high seas, where, if German, they will be taken as prize, or, if neutral, subjected to our contraband control’.
Although in late 1939 many of Churchill’s cabinet colleagues agreed with the need to take action to disrupt the iron ore traffic, they decided against the use of mines. At the time negotiations into the British chartering of the entire Norwegian mercantile shipping fleet were at a delicate stage and the British Foreign Office made convincing arguments against breaking Norway’s neutrality. In 1915 (during WWI) Britain had been forced to apologise to Norway for the violation of her territorial waters by British warships following the seizure of a German steamer inside the three mile limit. Near the end of WWI the British, Americans and French had induced the Norwegians to allow the Skjaergaard to be mined in order to prevent German ships and submarines from using their territorial waters as a way around the Great Northern Barrage, a massive minefield laid from Scotland to Norway as part of the earlier allied blockade strategy.
Despite the ongoing diplomatic exchanges, Britain informed the Norwegians that the Skjaergaard was about to be mined in January 1940, but the plan was postponed following protests from both Norway and Sweden. Yet another diplomatic dispute over alleged abuse of Norway’s territorial waters broke out in February 1940 between the respective governments of Britain, Norway and Germany following the Altmark Incident. A German tanker, attempting to return home via the cover of the Norwegian Corridor carrying British prisoners of war was spotted by British aircraft and pursued by destroyers, eventually being forced onto rocks.
On the evening of 21 March 1940 the British submarine HMS Ursula, (which had damaged the German cruiser Leipzig in Heligoland Bight the previous December) intercepted the German iron ore ship Hedderheim, en route from Narvik, and sank her eight miles off the coast of Denmark, although the crew were all saved. At the time it was seen as an early indication that Britain was at last taking steps to end the iron ore trade and over the next few days several other German ships were sunk at the entrance to the Baltic. Following reports that strong British destroyer and submarine forces were stationed in the Skagerrak, Berlin ordered all her ships along the iron ore route to port immediately.
By now it was clear to all concerned that the Phoney War was about to end. Antagonized by the German mining of their own waters with deadly new magnetic mines and a general concern that Germany was managing to overcome the worst effects of the blockade, the Supreme War Council met in London on 28 March 1940 to discuss an intensification of the economic warfare strategy.
Finally, on 3 April the War Cabinet gave authorization for the mining of the Skjaergaard. On the morning of Monday 8 April 1940 the British informed the Norwegian authorities of its intentions, and despite Norwegian protests and demands for their immediate removal, the Royal Navy carried out Operation Wilfred. However, by the time it took place German preparations for the German invasion of Norway were well under way and because of this only one minefield was actually laid, in the mouth of Vestfjord leading directly to Narvik.
Planning the Invasion
Convinced of the threat posed by the Allies to the iron ore supply, Hitler ordered Oberkommando der Wehrmacht (Armed Forces High Command; OKW) to begin preliminary planning for an invasion of Norway on 14 December 1939. The preliminary plan was named Studie Nord and only called for one army division.
Between 14 and 19 January, the Kriegsmarine developed an expanded version of this plan. They decided upon two key factors: that surprise was essential to reduce the threat of Norwegian resistance (and British intervention); the second to use faster German warships, rather than comparatively slow merchant ships, as troop transports. This would allow all targets to be occupied simultaneously, as transport ships only had limited range. This new plan called for a full army corps, including a mountain division, an airborne division, a motorized rifle brigade, and two infantry divisions. The target objectives of this force were the following:
- The Norwegian capital Oslo and nearby population centres
The plan also called for the rapid capture of the kings of Denmark and Norway in the hopes that would trigger a rapid surrender.
On 21 February 1940, command of the operation was given to General Nikolaus von Falkenhorst. He had fought in Finland during the First World War and was familiar with Arctic warfare. But he was only to have command of the ground forces, despite Hitler’s desire to have a unified command.
The final plan was code-named Operation Weserübung (“Exercise on the Weser“) on 27 January 1940. The ground forces would be the XXI Army, including the 3rd Mountain Division and five infantry divisions, none of the latter having yet been tested in battle. The initial echelon would consist of three divisions for the assault, with the remainder to follow in the next wave. Three companies of paratroopers would be used to seize airfields. The decision to also send the 2nd Mountain Division was made later.
Almost all U-boat operations in the Atlantic were to be stopped in order for the submarines to aid in the operation. Every available submarine—including some training boats—were used as part of Operation Hartmut in support of Weserübung.
Initially, the plan was to invade Norway and to gain control of Danish airfields by diplomatic means. But Hitler issued a new directive on 1 March that called for the invasion of both Norway and Denmark. This came at the insistence of the Luftwaffe to capture fighter bases and sites for air-warning stations. The XXXI Corps was formed for the invasion of Denmark, consisting of two infantry divisions and the 11th motorized brigade. The entire operation would be supported by the X Air Corps, consisting of some 1,000 aircraft of various types.
In February, the British destroyer HMS Cossack boarded the German transport ship Altmark while in Norwegian waters, thereby violating Norwegian neutrality, rescuing POWs held also in violation of Norwegian neutrality (the Altmark was obliged to release them as soon as she entered neutral territory). Hitler regarded this as a clear sign that the UK was willing to violate Norwegian neutrality, and so became even more strongly committed to the invasion.
On 12 March, the United Kingdom decided to send an expeditionary force to Norway just as the Winter War was winding down. The expeditionary force began boarding on 13 March, but it was recalled—and the operation cancelled—with the end of the Winter War. Instead, the British cabinet voted to proceed with the mining operation in Norwegian waters, followed by troop landings.
The first German ships set sail for the invasion on 3 April. Two days later, the long-planned Operation Wilfred was put into action, and the Royal Navy detachment—led by the battlecruiser HMS Renown—left Scapa Flow in order to mine Norwegian waters. The mine fields were laid in the Vestfjorden in the early morning of 8 April. Operation Wilfred was over, but later that day, the destroyer HMS Glowworm—detached on 7 April to search for a man lost overboard—was lost in action to the German heavy cruiser Admiral Hipper and two destroyers belonging to the German invasion fleet.
On 9 April, the German invasion was under way and the execution of Plan R 4 was promptly started.
Invasion of Denmark
Strategically, Denmark’s importance to Germany was as a staging area for operations in Norway, and of course as a border nation to Germany which would have to be controlled in some way. Given Denmark’s position in relation to the Baltic Sea, the country was also important for the control of naval and shipping access to major German and Soviet harbours.
The German plans for the invasion and occupation of Norway relied heavily on air power. In order to secure the Skagerrak strait between Norway and Denmark, the air bases in Denmark had to be seized. The domination of this strait would prevent the Royal Navy from interfering with the main supply lines of the invasion forces. In this respect, the occupation of Denmark was considered to be vital. The capture of Aalborg Airport was considered as particularly important in this respect.
Small and relatively flat, the country was ideal territory for German army operations, and Denmark’s small army was significantly smaller than the Werhmacht. Nevertheless, in the early morning hours, a few Danish troops engaged the German army, suffering losses of 16 dead and 20 wounded. The Germans lost 203 soldiers, together with 12 armored cars and several motorcycles and cars destroyed. Four German tanks were damaged. One German bomber was also damaged. Two German soldiers were temporarily captured by the Danes during the brief fighting.
At 04:00 on 9 April 1940, the German ambassador to Denmark— Cecil von Renthe-Fink—called the Danish Foreign Minister Peter Munch and requested a meeting with him. When the two men met 20 minutes later, Renthe-Fink declared that German troops were at that moment moving in to occupy Denmark to protect the country from Franco-British attack. The German ambassador demanded that Danish resistance cease immediately and contact be made between Danish authorities and the German armed forces. If the demands were not met, the Luftwaffe would bomb the capital, Copenhagen.
As the German demands were communicated, the first German advances had already been made, with forces landing by ferry in Gedser at 03:55 and moving north. German Fallschirmjäger units had made unopposed landings and taken two airfields at Aalborg, the Storstrøm Bridge as well as the fortress of Masnedø, the latter being the first recorded attack in the world made by paratroopers.
At 04:20 local time, a reinforced battalion of German infantrymen from the 308th Regiment landed in Copenhagen harbour from the minelayer Hansestadt Danzig, quickly capturing the Danish garrison at the Citadel without encountering resistance. From the harbour, the Germans moved toward Amalienborg Palace to capture the Danish royal family. By the time the invasion forces arrived at the king’s residence, the King’s Royal Guard had been alerted and other reinforcements were on their way to the palace. The first German attack on Amalienborg was repulsed, giving Christian X and his minister’s time to confer with the Danish Army chief General Prior. As the discussions were ongoing, several formations of Heinkel He 111 and Dornier Do 17 bombers roared over the city dropping the OPROP! leaflets.
At 05:25, two squadrons of German Bf 110s attacked Værløse airfield on Zealand and wiped out the Danish Army Air Service by strafing. Despite Danish anti-aircraft fire, the German fighters destroyed ten Danish aircraft and seriously damaged another fourteen, thereby wiping out half of the entire Army Air Service.
Faced with the explicit threat of the Luftwaffe bombing the civilian population of Copenhagen, and only General Prior in favour of continuing to fight, the King Christian X and the entire Danish government capitulated at approximately 06:00 in exchange for retaining political independence in domestic matters.
The invasion of Denmark lasted less than six hours and was the shortest military campaign conducted by the Germans during the war. The rapid Danish capitulation resulted in the uniquely lenient occupation of Denmark, particularly until the summer of 1943, and in postponing the arrest and deportation of Danish Jews until nearly all of them were warned and on their way to refuge in Sweden. In the end, 477 Danish Jews were deported, and 70 of them lost their lives, out of a pre-war total of Jews and half-Jews at a little over 8,000.
Though Denmark had little immediate military significance, it had strategic and to some extent economic importance.
Invasion of Norway
Motivation and order of battle
Norway was important to Germany for two primary reasons: as a base for naval units, including U-boats, to harass Allied shipping in the North Atlantic, and to secure shipments of iron-ore from Sweden through the port of Narvik. The long northern coastline was an excellent place to launch U-boat operations into the North Atlantic in order to attack British commerce. Germany was dependent on iron ore from Sweden and was worried, with justification that the Allies would attempt to disrupt those shipments, 90% of which originated from Narvik.
- 69th Infantry Division
- 163rd Infantry Division
- 181st Infantry Division
- 196th Infantry Division
- 214th Infantry Division
- two regiments of the 3rd Mountain Division
The initial invasion force was transported in several groups (Gruppe) by ships of the Kriegsmarine:
- Battleships Scharnhorst and Gneisenau as distant cover, plus 10 destroyers with 2,000 mountaineering troops under General Eduard Dietl to Narvik;
- Heavy cruiser Admiral Hipper and four destroyers with 1,700 troops to Trondheim;
- Light cruisers Köln and Königsberg, artillery training ship Bremse, transport Karl Peters, two torpedo boats and five motor torpedo boats with 1,900 troops to Bergen;
- Light cruiser Karlsruhe, three torpedo boats, seven motor torpedo boats and Schnellboot mothership (Schnellbootbegleitschiff) Tsingtau with 1,100 troops to Kristiansand and Arendal;
- Heavy cruiser Blücher, heavy cruiser (formerly pocket battleship) Lützow, light cruiser Emden, three torpedo boats and eight minesweepers with 2,000 troops to Oslo;
- Four minesweepers with 150 troops to Egersund.
The German invasion first started on 3 April 1940, when covert supply vessels began to head out in advance of the main force. The Allies initiated their plans on the following day, with sixteen Allied submarines ordered to the Skagerrak and Kattegat to serve as a screen and advance warning for a German response to Operation Wilfred, which was launched the following day when Admiral William Whitworth in HMS Renown set out from Scapa Flow for the Vestfjorden with twelve destroyers.
On 7 April, bad weather began to develop in the region, blanketing the area with a thick fog and causing rough seas making travel difficult. Renown’s force soon got caught in a heavy snowstorm, and HMS Glowworm, one of the destroyer escorts, had to drop out of formation to search for a man swept overboard. The weather aided the Germans, providing a screen for their forces, and in the early morning they sent out Gruppe 1 and Gruppe 2, who had the largest distance to travel.
Though the weather did make reconnaissance difficult, the two German groups were discovered 170 km (105 mi) south of the Naze (the southernmost part of Norway) slightly after 08:00 by Royal Air Force patrols and reported as one cruiser and six destroyers. A trailing squad of bombers sent out to attack the German ships found them 125 km (78 mi) farther north than they had been before. No damage was done during the attack, but the German group’s strength was reassessed as being one battlecruiser, two cruisers and ten destroyers. Because of a strict enforcement of radio silence, the bombers were not able to report this until 17:30.
On learning of the German movement, the Admiralty came to the conclusion that the Germans were attempting to break the blockade that the Allies had placed on Germany and use their fleet to disrupt Atlantic trade routes. Admiral Sir Charles Forbes, Commander-in-Chief of the British Home Fleet, was notified of this and set out to intercept them at 20:15.
With both sides unaware of the magnitude of the situation, they proceeded as planned. Renown arrived at the Vestfjord late that night and maintained position near the entrance while the minelaying destroyers proceeded to their task. Meanwhile, the Germans launched the remainder of their invasion force. The first direct contact between the two sides occurred the next morning without either side’s intention.
British destroyer HMS Glowworm, on its way to rejoin HMS Renown, happened to come up behind German destroyer Z11 Bernd von Arnim and then the Z18 Hans Lüdemann in the heavy fog around 08:00 on 8 April. Immediately a skirmish broke out and the German destroyers fled, signaling for help. The request was soon answered by the pocket battleship Admiral Hipper, which quickly crippled Glowworm. During the action, Glowworm rammed Admiral Hipper. Significant damage was done to Hipper’s starboard, and Glowworm was destroyed by a close range salvo immediately afterwards. During the fight Glowworm had broken radio silence and informed the Admiralty of her situation. She was not able to complete her transmission though, and all the Admiralty knew was that Glowworm had been confronted by a large German ship, shots were fired, and contact with the destroyer could not be re-established. In response, the Admiralty ordered Renown and her single destroyer escort (the other two had gone to friendly ports for fuel) to abandon her post at the Vestfjord and head to Glowworm’s last known location. At 10:45, the remaining eight destroyers of the minelaying force were ordered to join as well.
In the morning of 8 April, the Polish submarine ORP Orzeł confronted and sank the clandestine German troop transport ship Rio de Janeiro off the southern Norwegian port of Lillesand. Amongst the wreckage were discovered uniformed German soldiers and various military supplies. Though Orzeł reported the incident to the Admiralty, they were too concerned by the situation with Glowworm and the presumed German breakout to give it much thought and did not pass the information along. Many of the German soldiers from the wreck were rescued by Norwegian fishing boats and the destroyer Odin. On interrogation the survivors disclosed that they were assigned to protect Bergen from the Allies. This information was passed on to Oslo where the Norwegian Parliament ignored the sinking due to being distracted by the British mining operations off the Norwegian coast.