'Arno' was a German naval operation to escort blockade runners, inbound from Japan, to a French port in an undertaking that also involved 'Sacco' for the escort of outbound blockade runners from French ports (March/April 1943).

At this time the blockade runners Regensburg, Pietro Orseolo, Karin and Irene were heading north through the northern part of the South Atlantic with Weserland to their south and both Rio Grande and Burgenland still in the Indian Ocean on passage to round the Cape of Good Hope.

Karin was ordered to dally in the South Atlantic, where she was soon scuttled as US warships approached her, as preparations were made to escort Pietro Orseolo through the Bay of Biscay toward a port on the west coast of German-occupied France while Regensburg and Irene headed north to pass Iceland and reach ports in German-occupied Norway.

The German escort to Bordeaux was provided by the fleet destroyers Z 23, Z 24, Z 32 and Z 37 of Kapitän Hans Otto Erdmenger’s 8^th Zerstörer-Flottille, and Pietro Orseolo reach Bordeaux on 2 April.