German U-boats (submarines) started being used as weapons of war during World War I. On 7 Oct. 1916 U-53 stopped at Newport, RI and visited with a couple of US Admirals. As that the US had nor entered the war, the sub was to peacefully leave. The very next day the sub sank 5 ships that it said were carrying contraband but not before allowing the crew of the ships to abandon the ships. The sub also did allow a couple of passenger ships to pass without incident. This same sub sank many more ships the next year. It was eventually captured in December 1918.
THE MONROE COUNTY MAIL
Thursday, Oct. 12, 1916
ONE SUB DID SINKING
U-Boat Was Very Fast and Was Cleverly Handled.
The wholesale raid on foreign shipping south of Nantucket lightship on Sunday was the work of one submarine, according to reports of American naval officers.
Rear Admiral Albert Gleaves, commanding the torpedo-boat destroyer flotilla, which did such remarkably speedy rescue work on Sunday, said that the reports of all officers agreed that one raider only was concerned.
Admiral Gleaves said he could easily understand the positive statements of the captain of the Nantucket lightship and of sailors of the torpedoed vessels that more than one submarine was concerned. The U-boat, he said, was very fast and appeared to have been handled cleverly.
It was easy, he pointed out, for her to disappear on one side of a ship and then show up unexpectedly at another spot.
Doubtless, he believed, she had submerged and reappeared often enough to mislead any but a keen professional observer and to create the impression that more than one sea terror was operating.
This opinion would seem to be borne out by the statements of many of the refugees that the submarine had more business on hand than she could take care of at once and was obliged to request one steamer, to wait her turn while another was being put out of commission.
Later news from Newport says that the German commerce raiders that bore down on shipping off the New England coast on Sunday, sending six vessels to the bottom, are believe to have made a clean escape.
British warships from the American coast patrol and from Canadian ports are still scoring the Atlantic far out at sea in hopes of overtaking the Germans.