This was a British naval undertaking within ‘Cosmic’ to concentrate a sizeable force of British submarines off the coast of German-occupied Norway on receipt of intelligence suggesting that the Germans were about to send the battleship Tirpitz to sea (16/late March 1944).
On 16 March the Free Dutch Zwaardvis departed for the Gimsöströmmen, British Syrtis and Taku for the Kya area, Satyr and Vox to Stadlandet, Free Norwegian Ula to Bredsund, and British Trusty and Vivid to Skudesnes. On 18 March Safari, Sturdy, Terrapin, Truant, Una, Unbending, Unbroken and Free Dutch Zeehond departed Lerwick for Norwegian waters.
Then on 20 March it started to become clear that the Germans might not be moving Tirpitz, so Safari, Truant, Una, Unbroken, Vivid, Zeehond and Zwaardvis were ordered back to base. Syrtis was redirected to Bodø, where on 22 March it sank the 214-ton Norwegian Narvik before being lost to a mine six days later. Ula was despatched against the liner Monte Rosa, which was being moved to the north as an accommodation ship for repair work on Tirpitz, but was not able to effect an interception, and on 21 March missed a convoy. Off Namsos, Taku missed a motor vessel on 24 March, but on the same day Satyr sank the 340-ton Norwegian Nord Norge, and Terrapin torpedoed and damaged the 6,256-ton tanker Worth and the 8,186-ton catapult ship Schwabenland, both of which had to be run aground in the Flekkefjord to prevent them from sinking.