This was the German capture of Oslo, the capital of Norway, by the forces of Konteradmiral Oskar Kummetz’s Gruppe V, within ‘Weserübung’ (9/10 April 1940).
Gruppe V comprised the heavy cruiser Blücher, pocket battleship Lützow, light cruiser Emden, torpedo boats Albatros, Kondor and Möwe, and 14 minesweepers and smaller vessels, and these transported and landed elements of Generalmajor Hermann Tittel’s 69th Division and Generalmajor Erwin Engelbrecht’s 163rd Division.
Gruppe V met the most serious resistance at the inner defensive fortifications of the Oslofjord, in the vicinity of Drøbak. Leading the group, Blücher approached the forts on the tactical assumption that these would be taken by surprise and therefore not be be able to make a timely response, like many others in the outer part of the fjord. It was not until the cruiser was at point-blank range that the three 11-in (280-mm) guns of the Oscarsborg fortress opened fire, belying their half-century age and obsolescence by obtaining hits with every shot. Within a matter of minutes Blücher was crippled and burning heavily, and the damaged warship was soon finished off by a salvo from land-based torpedo tubes, sinking the ship, which carried most of the administrative and security personnel intended for the administration of captured Norway, and also the headquarters staff of the army formations assigned to seize Oslo.
Also damaged in the attack and believing the Blücher had entered a minefield, Lützow turned back with the rest of Gruppe V some 12 miles (19 km) to the south toward Sonsbukten, where the embarked troops were unloaded. The distance the troops had to advance delayed the arrival of the main German invasion force for Oslo by more than 24 hours, though Oslo was nonetheless captured less than 12 hours later by troops flown into the nearby airport and base at Fornebu.
The defence of Oslo was provided by the Royal Guards battalion based in Oslo and Elverum, Major General Carl J. Erichsen’s 1st Division (1st, 2nd and 3rd Regiments, 1st Cavalry Regiment and 1st Artillery Regiment) and Major General Jacob Hvinden Haug’s 2nd Division (4th, 5th and 6th Regiments, 2nd Cavalry Regiment and 2nd Artillery Regiment).
The German plan called for Fornebu to be taken by the airborne assault of a paratroop company of Major Erich Walter’s 1/1st Fallschirmjägerregiment of Generalleutnant Kurt Student’s 7th Fliegerdivision before the first air-landed troops were delivered. The delay to the main part of the assault force therefore placed greater emphasis on the need for success in this airborne part of the operation. But adverse weather hit the Oslo transport force, which comprised 29 Junkers Ju 52/3m aircraft. After two of his aircraft had collided in the thick overcast, the transport force commander reluctantly decided to turn back without dropping the paratroopers.
A considerable dispute followed back at base when this information was received by radio, but eventually the air commander ordered all his forces to turn back. At that moment, though, Hauptmann Wagner, in command of the leading element of the transport force, arrived over Fornebu airfield. Suspecting perhaps that the order to turn back was a Norwegian trick, Wagner decided to press on with the original plan. As his aeroplane came in to land it was hit by machine gun fire and Wagner was killed. The co-pilot took over and decided to turn back.
Thus the whole assault force was now on its way back to Germany, despite the fact that one part of it at least had attempted to land the paratroops rather than drop them. Over Fornebu were six Messerschmitt Bf 110 two-engined heavy fighters to support the airborne forces and then land on the captured airfield. Now very short of fuel, their commander decided that the aircraft would land and their rear gunners would attempt to hold off the Norwegians with machine gun fire until another force could be flown in after the weather had improved. One Bf 110 crashed on landing, but the other five got down successfully and adopted the best defensive positions they could.
The crews of the German fighters were then amazed to discover that the Norwegians had pulled out, leaving the airfield in the hands of the German fighters.
By 09.15 a few Ju 52/3m transports arrived and disgorged their paratroops, and throughout the morning other transports arrived, after refuelling, to bring in more paratroops. Yet the German garrison on the airfield was tactically very vulnerable, and was saved only by the paralysis the new German offensive method had inflicted on the Norwegians.
The pilots of the Norwegian fighter wing based at Fornebu resisted with their Gloster Gladiator biplane fighters until they had exhausted their ammunition, and then flew their aircraft to whatever secondary airfields were available. The ground personnel of the fighter wing soon ran out of ammunition for their anti-aircraft guns, and in the general confusion of getting the fighters into the air no one had issued ammunition for the small arms of the ground personnel. Resistance at Fornebu therefore ended quickly, and Norwegian attempts to mount a counterattack came to nothing.
With the arrival of the first elements of the 163rd Division’s 324th Regiment, the German hold on the airfield became better assured, but the German commander then decided to advance on Oslo with some six companies of infantry, which was by any objective criterion a hopelessly inadequate force. Moving swiftly, and with a military band giving the force the appearance of assured conquerors, the force moved on Oslo, which was immediately declared an open city.
However, the delay in the German occupation of Oslo provided the Norwegians with the time to evacuate the royal family, parliament and national gold reserves to points still out of the reach of the Germans.
While the three major warships whose target was Oslo were supported by the motor minesweepers R 8, R 18 and R 19, there were also four subgroups carrying assault forces for the capture of smaller objectives: the torpedo boat Möwe was directed against Son and Moss, the torpedo boats Albatros (grounded and wrecked 10 April while under fire from Norwegian coastal artillery) and Kondor as well as the motor minesweepers R 7, R 17 (sunk by the Norwegian minelayer Olav Tryggvason and minesweeper Rauma) and R 22 against Horten, the motor minesweepers R 20 and R 24 against Rauøy island, and the motor minesweepers R 22 and R 23 against Bolearne island.