The Royal Navy submarine HMS Sturgeon was patrolling between Denmark and Norway when she spotted a military transport being escorted by smaller craft. It was the 3624 tonne troopship Pionier taking troops to Norway. The log of the Sturgeon records:
At 19.39 a large transport could be seen escorted by a “T”-class torpedo boat on either bow. There were some smaller vessels astern. Two torpedoes were fired at 19.53 from a range of 6000 yards. The target was silhouetted against the sun. One explosion was heard at 19.58 and when the periscope was raised a dense column of black smoke was seen rising from the target to a height of about 2000 feet. The small vessels astern of “Pionier” scattered and no attack on them was possible. “Sturgeon” went deep to reload her torpedo tubes at 21.15 and at that time “Pionier” was burning furiously and settling low in the water.
When HMS Sturgeon surfaced at 22.30 the ‘Pionier’ had disappeared.