Immediate attack in any manner available is permitted by submarines against enemy merchant vessels which are obviously armed or have been proclaimed as such on the basis of conclusive evidence received by the Naval War Staff. As far as circumstances permit, measures are to be taken to save the crew after every possibility of danger for the submarine has been eliminated. Passenger ships not used to transport troops are still not to be attacked, even if armed. The excerpt below shows the transmission of the order to the submarines. The document was issued before May, 1940.
Further details follow.
Experiences drawn from the entire operations of the British Merchant Service are summarised in the next document in an order. It has been numbered Donitz 66, and is on Page 161. I shall read the order which is dated 17th October, 1939. On Page 162 I have reproduced another part of document Donitz 62, which has been submitted already. In the next, the German government warns neutral nations against the use of enemy ships for this reason.