It ended up being the second most successful U-boat participating in the war, sinking 149 merchant ships for a total of 404,774 GRT.

Its longest-serving captain was Kapitänleutnant Walther Forstmann, who was awarded the Pour le Mérite during command on U-39.

He later became Grand Admiral and Commander in Chief of the German Navy, and, for three weeks following Hitler's death, the head of the remnants of the Nazi government.

On 17 May, together with SM UB-50, U-39 operated against a convoy North of Oran, from which it sank the British steamer Sculptor (4,874 GRT) in a submerged attack.

It crash-dived, but when reaching a depth of 12 meters two bombs exploded very close; the after torpedo room flooded, the diving planes were destroyed, and the boat began sinking by the stern.

At about 17:00, U-39 was attacked again by two seaplanes; it fought back with gun and machine-guns, and the enemy bombs caused no damage, but during the action two crewmen (sailor Schulz and stoker Hausottl) fell overboard and were lost.