Its operations were in June 1940, at the beginning of the "Happy Time", when the U-boat Arm renewed its offensive in the Atlantic campaign.
In June 1940 U-boat Command (BdU) received intelligence that a large troop convoy would be passing through the mid-Atlantic to Britain.
[1] The convoy, designated US 3, would comprise seven troopships, including RMS Queen Mary and would be transporting some 25,000 Australian and New Zealand troops.
It was decided to form a patrol line off the coast of Spain, in order to mount a wolf pack attack on the convoy.
Sailing independently, the five boats of Rösing's pack achieved great success, sinking a total of 27 ships.