SM U-156 was a German Type U 151 U-boat commissioned in 1917 for the Imperial German Navy. Built by Atlas Werke in Bremen, U-156 was originally conceived as one of seven Deutschland-class cargo U-boats designed for transatlantic supply, but five of these, including U-156, were converted into long-range cruiser U-boats equipped with two 15 cm (5.9 inch) SK L/45 deck guns, making it the largest U-boat class of World War I. Launched on 17 April 1917 and commissioned on 22 August 1917, U-156 was commanded initially by Konrad Gansser and later by Richard Feldt. The vessel had a notable service record, sinking 45 ships and damaging two others during her operational lifetime. Her missions included patrolling the North Atlantic, laying mines, and engaging enemy vessels. U-156 is perhaps best known for her attack on Orleans, Massachusetts, on 21 July 1918—the only wartime shelling of the U.S. mainland by enemy fire. During this raid, she damaged a tugboat and sank four barges, while American aircraft unsuccessfully bombed her with bombs that failed to explode. This event marked the first engagement of American aviators with an enemy vessel in the western Atlantic and was the only instance of the Continental United States being shelled by a foreign power during World War I. The submarine also conducted extensive operations along the U.S. East Coast, sinking numerous fishing boats in the Gulf of Maine, including the schooner Nelson A. and the Dornfontein. She was credited with sinking the tanker Luz Blanca near Halifax and capturing the Canadian trawler Triumph, which she used to assist in sinking several other fishing vessels. U-156's final mission involved passing through the Northern Barrage minefield between the UK and Norway. Presumed to have struck a mine during her return voyage in September 1918, the submarine and her 77 crew members disappeared without further contact. Her loss marked the end of her notable career, and she remains a significant vessel for her daring operations and the only instance of U-boat shelling on U.S. soil during the war.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.