'Amsel I' was a U-boat wolfpack operation, in tandem with 'Amsel II', 'Specht' and 'Star', in the Atlantic (4/6 May 1943).

The wolfpack comprised U-267, U-402, U-504, U-575, U-621 and U-638, and for the loss of Kapitänleutnant Oskar Staudinger’s U-638 sank the 5,507-ton British Dolius in an attack on the ONS.5 convoy, which lost a total of 13 ships (61,958 tons).

Sailing in ballast, Dolius was torpedoed and sunk about 445 miles (715 km) to the east-north-east of Belle Isle. Three crew members and one gunner were lost, while her captain, 57 crew members and eight gunners were rescued by the British corvette Sunflower, which had just sunk U-638, and landed at St John’s, Newfoundland.