Early WW2, submarines routinely surfaced after sinking a ship, and would provide compasses, water, food, etc. to people in the life boats,
However, off West Africa Africa, a German U boat had sunk a British Troop ship, the Laconia, carrying over 2400 people. The German sub surfaced, collected life boats, and started towing them to a transfer point. It broadcast it's position and plans on the international humanitarian channels.
Basically, until it relieved itself of all the people, it was a non combatant ship. The deck of the submarine had over 400 people on it, and it was flying Red Cross Colors.
While towing, it was spotted by an American bomber, who, was given orders, even though it was a non combatant, to attack it. The bomber killed a lot of people, mostly British soldiers. The German sub dove, and abandoned the 1000+ people in the ocean.
After that, the Germans would no longer assist survivors. Close to this time, it was found out that a British sub had massacred survivors of a German ship sunk.
At the post WW2 trials, one of the prosecution areas was on German War crimes on the high seas, and specifically the point that the Germans had an order to ignore survivors on the high seas. When the back story came out, it put the Americans and British in the position of trying to prosecute the Germans for what had been started by the Americans and Brits, so they dropped it
ed ay +3112
1968 GT500 Arrest Me Red (The Big Boy Toy)
1966 K Code Vert (The K 'Vert)