Home / Editors Picks / The German Mine Laying Campaign off the Coast of America
USS San Diego (Armored Cruiser No. 6) Painting by Francis Muller, 1920. It depicts the ship sinking off Fire Island, New York, after she was torpedoed by the German submarine U-156, 19 July 1918.

The German Mine Laying Campaign off the Coast of America

By Chris Martin, Historian, Naval History and Heritage Command

Editor’s note: July 19, 2018 marks 100 years since the sinking of USS San Diego. In the naval history world, the sinking is fairly well known, however the loss, and its proximity to the coast of Long Island, New York, may be forgotten by most Americans today. For the 100th anniversary, Naval History and Heritage Command (NHHC) will share the story of the ship and hopes to answers some unknowns about its sinking. To provide necessary context, we asked NHHC Historian Chris Martin how were German submarines able to get so close to our shores during WWI? How were they able to sink USS San Diego?

USS San Diego (Armored Cruiser No. 6) Painting by Francis Muller, 1920. It depicts the ship sinking off Fire Island, New York, after she was torpedoed by the German submarine U-156, 19 July 1918.


The Start of German Operations off America’s Coast

On July 19th, 1918, the 15,138-ton armored cruiser San Diego sank 10.5 miles southeast of Fire Island, NY, killing six sailors. San Diego was the only major warship lost by the U.S. Navy during World War I and the loss of San Diego in calm seas so close to the American coastline rattled the American public and could have given the German Imperial Navy a moral victory over the U.S. Navy that they had been unable to achieve in over a year of direct conflict.

Chief of Naval Operations Admiral William S. Benson.

Shortly after the United States entered World War I on April 6th, 1917, Vice Admiral William S. Sims, the Commander of the United States Forces in Europe cabled Chief of Naval Operations Admiral William S. Benson with news that the German Navy would likely deploy a limited number of U-boats to the American coastline. According to Sims, the German Navy believed that if their U-boats destroyed enough American domestic commercial shipping, American public opinion would force the U.S. Navy to recall ships from the European theater and assign them to domestic convoy protection. Sims warned Benson that such a diversion of assets out of the war zone would be a huge mistake. A little over a month later, the arrival of the first U-boat off the East Coast tested the American commitment to Europe and the Navy’s pre-war planning.

On April 18th, 1918, U-151 deployed from Kiel, Germany bound for the American coastline. Despite information provided by British intelligence to Admiral Sims on  May 1st, the Navy was unable to locate U-151 until May 19th, when the American steamship Nyanza reported that she was under attack by a German U-boat approximately 300 miles off the coast of Maryland. Subsequent reports sent by American merchant steamers indicated U-151 was headed to the mouth of the Chesapeake Bay. On May 22nd U-151 laid the first minefields on the East Coast. One in the mouth of the Chesapeake and another in the Delaware Bay. On June 1, the Germans sunk a merchant vessel, Texel, from their mine-laying campaign. The steamship Texel sank during its voyage from Puerto Rico to New York. Two days later, on June 3rd, the Texel’s crew reached shore in Atlantic City, New Jersey and reported two U-boats were off the American coast. Unknown to the Americans, U-151 had already begun its journey back to Kiel, Germany.

German Submarine U-151, the type of U-boat that operated in American waters during WWI.


America’s Solution to German Mines: Escorts

To reassure the American public, the U.S. Navy issued a public statement describing the Germans U-boat campaign as one designed to manipulate Americans into forcing the recall of ships from the European theater. The Navy also activated a plan that placed domestic coastal shipping into convoys escorted by Navy submarine chasers. Prior to each voyage, merchant ships received written instructions on the route to be followed, potential hazards, and the locations of communications stations set up by the Navy to convey the latest information ships needed along their route. Lastly, Navy organized a small offensive U-boat hunting squadron led by the destroyer Jouett (DD 41) supported by submarine chasers. With multiple defensive measures in place, U-boats deployed to the American coastline between mid-June and early-September 1918 were content to lay mines and attack a handful of unescorted merchant ships.

Led by Kapitänleutenant Richard Feldt, U-156 deployed from Kiel on 16 June with orders to lay a minefield across the approach to New York Harbor. Again, aided by British intelligence, Sims cabled Benson in advance of the boat’s arrival in American waters. The Navy subsequently issued a statement to the American public about U-156 on June 26th. On July 5th, U-156 engaged the mine carrier Lake Bridge, transporting American mines destined for the North Sea Mine Barrage, in a 30-minute artillery battle. Lake Bridge eventually outran her pursuer. On July 7-8, U-156 sunk two Norwegian merchant ships steaming out of New York Harbor. Because U-156 was later lost at sea, little is known about her whereabouts during the day leading up to San Diego’s sinking. However, on July 17th, just two days before San Diego would sink, the troop transport Harrisburg reported sighting a U-boat south of Nantucket, Massachusetts. This unconfirmed sighting led the U.S. Navy to conclude after the war that U-156 laid the minefield that sank San Diego.

While the actual cause of the San Diego’s sinking is still being studied, on September 6th, Feldt sent a wireless radio report to Germany claiming that his boat, U-156, sunk 41,000 tons of allied shipping, including San Diego.

Altogether, during WWI, four more U-boats, U-140, U-117, U-155 and U-152 deployed to the American coast. Overall, the German U-boat campaign sank 91 ships off the East Coast totaling 166,907 tons. Stay tuned as we commemoration the loss of USS San Diego throughout the week.