Empire Endurance was a 8,514 GRT steam cargo liner that was built in 1928 as Alster by Deschimag Werk Vulkan, Hamburg, Germany for the shipping company Norddeutscher Lloyd.

In the years leading up to the Second World War Alster carried cargo and passengers between Germany and Australia.

Initially serving under the original name as a repair, supply and cargo ship in Norway, she was later passed to the Ministry of War Transport (MoWT) and renamed Empire Endurance.

She served until 20 April 1941 when she was torpedoed and sunk by the German submarine U-73 south-east of the islet of Rockall in the North Atlantic Ocean.

Via double-reduction gearing and a Föttinger fluid coupling the turbine drove the same shaft as the piston engine.

[17][18] While at Kopervik, Alster and Kattegat were inspected by the torpedo boat HNoMS Stegg, the Norwegians finding nothing irregular.

[18] By 8 April, Alster had reached Vestfjorden, where she was hailed by the Norwegian patrol boat HNoMS Syrian, which warned her of the British naval minefield laid in the area earlier that day.

When Syrian found Alster, the commander of the small Norwegian patrol boat chose not to board the German vessel as he suspected she was armed and possibly carrying troops.

When intercepted the German crew made an unsuccessful attempt at scuttling the vessel, setting off one explosive charge.

[25] With the British capture of Alster, no more German supply ships were heading for Narvik and the forces there,[26] leaving General Eduard Dietl's troops with the supplies on board the tanker Jan Wellem and the large stockpiles of weapons, ammunition, uniforms and food captured at the Norwegian Army base Elvegårdsmoen.

[30] At Skjelfjord, the captured German crew made an unsuccessful attempt at scuttling Alster by opening the ship's sea valves.

One of the vessels on which emergency repairs were carried out from Alster, was the destroyer HMS Eskimo, which had lost her bow during the naval battles off Narvik.

[33] On 24 April Alster departed Skjelfjord for the Northern Norwegian port of Tromsø, manned by a British prize crew.

[35] Her cargo of 88 lorries, anti-aircraft guns, spare parts for aircraft, ammunition, communications equipment, coke and 400–500 tons of hay, was unloaded in Tromsø on 27 April, as part of the Allied support of the Norwegian forces fighting the German invasion of their country.

The cargo was put to use in the supply and defence of the Tromsø area, except for the hay, which was quarantined by the Norwegian authorities at Ringvassøy for fear of foot-and-mouth disease.

[35] On 16 May a request was made to the Admiralty for a call sign for Alster, the ship departing Tromsø the next day for Kirkenes in Finnmark, escorted by the anti-submarine whaler HMS Ullswater.

Arriving on 19 May 1940, Alster loaded some 10,000 tons of iron ore over four days, sailing south to the port of Harstad on 22 May, still escorted by HMS Ullswater, as well as the Norwegian patrol boat HNoMS Nordhav II.

During one of the attacks on 26 May the ship's Norwegian fireman was mortally wounded by bomb fragments, dying in Harstad Hospital later the same day.

[7] Empire Endurance sailed in Convoy FN 255, which left Southend, Essex on 17 August and arrived at Methil, Fife two days later.

Empire Endurance sailed on 12 September for Sydney, Cape Breton, Nova Scotia, arriving three days later.

[56] She then joined Convoy HX 74, which departed from Halifax, Nova Scotia on 17 September and arrived at Liverpool, Lancashire, United Kingdom on 2 October.

[56] On 19 April, Empire Endurance departed from Milford Haven,[56] bound for Cape Town, South Africa and Alexandria, Egypt.

At 03:32 (German time) on 20 April, Empire Endurance was hit amidships by a torpedo fired by U-73, under the command of Helmut Rosenbaum.