U-boat Assault on America: The Cruise of U-156

U-155, Class Sister of U-156, on Display in London
Postwar. Note Twin Deck Guns and Wide Hull to Carry
Cargo or Supplies

In earlier articles on Roads we have discussed the 1917–1918 U-boat assault on America during the First World War, HERE and HERE.  Our source article for these two articles focused on three U-boats that were active off the Atlantic Coast  (U-117, U-140, and U-151).  These boats were quite successful sinking or disabling over 50 Allied vessels during their time on station off of Canada and the U.S. They inflicted the damage via surface and torpedo attacks, by laying mines, or destroying vessels by various means after forcing their crews to stop and abandon ship. 

There was, however, a fourth U-boat, the U-156—specially designed for long-range operations—that also wrecked similar destruction and has also been officially credited by the U.S. Navy with sinking—by minelaying—one of the two U.S. Navy combat vessels lost during the war, the 13,680 ton armored cruiser USS San Diego.  [A little personal note here. The USS San Diego—originally the USS California—was built at San Francisco's Union Iron Works while my grandfather Tom Stack was working there.]

USS San Diego,  Lost 19 July 2018

The initial investigation on the sinking of the cruiser concluded a mine had caused its sinking. Over the years, however, other theories emerged involving a torpedo attack or sabotage.  These suggestions raised enough doubts to trigger another very well resourced study a century after the San Diego was lost.  The online Smithsonian magazine of 14 December 2018 summarized the results:

. . . A team of investigators from 10 government agencies and academic institutions spent the past two years researching to find the conclusive answer. Using archival documents, as well as 3D scans of the shipwreck, the team was able to create sophisticated models of how the ship flooded and how the explosion impacted its hull. Ken Nahshon, research engineer at the Naval Surface Warfare Center Carderock Division, tells Niiler that the results are consistent with hitting a mine. The flooding model also shows that the design of the ship’s coal storage compartments probably led to its quick sinking, not mistakes by the crew.

This story of the USS San Diego's sinking, as well as the story of the subsequent rampage by the U-156 has been somewhat neglected over the years. For the cruiser, this might have been because the loss of life for the ship was relatively low for the sinking of a large warship—six killed and six injured—or because it was late in the war when the nation's eyes were focused on the Western Front. As for U-156, its subsequent operations mainly focused on an odd, undramatic selection of targets (discussed below), and it was mysteriously lost at sea, and hardly anyone noticed it was gone at the time.

The U-156 and Its North American Mission

U-156 Commander, Kapitänleutnant Richard Feldt

U-156 was launched in April 1917 at the Atlas Werke in Bremen. It conducted two patrols during the war, the last under the command of Kapitänleutnant Richard Feldt to the coast of North America.  It subsequently was lost with all hands (77 men) on 25 September 1918. Like USS San Diego, it is believed that U-156 was destroyed by a mine.

As for  U-156’s activities the following is known. En route to the East Coast of America,  Skipper Richard Feldt stumbled across several targets of opportunity. Northwest of Scotland his U-boat stumbled across the unlucky 4,000 ton steamer Tortuguero and sank it. Later on, two iron-hull sailing vessels, the Marosa and the Manx King, met the same fate, but the main mission involved hunting along the Canadian and American coast. After arriving on station, the mines that sank the San Diego were laid apparently.   

U-156's subsequent record of sinkings seems to reflect a strategy of starving out America by attacking  the mostly small vessels of its coastal trading and fishing fleets. This period of warfare involved the sinkings of five vessels that most people would consider "ships" (four small freighters and one tanker).  The U-boats remaining list of  sinkings include one tugboat, six small cutters or barges, and 19 fishing boats and trawlers. This might have pleased the captain and crew and resulted in a lot of decals added to the conning tower, but the large number of sinkings seems more a tribute to the industriousness of Kapitänleutnant Feldt.  Committing one of Germany's most technologically advanced vessels to hunt fishing boats seems a misdirection of resources. It was, though, something of humanitarian accomplishment by Feldt that he managed to sink over 30 vessels while inflicting only six casualties among all their crews.

Fishing Sloop E.B.Walters, Sunk by U-156,
25 August 1918

Such was the mission and fate of the last World War I U-boat to attack the American coast in World War I. Its successors would return in the next war, however, seeking juicier targets and making a much bigger impact in 1942.

Sources: "The U.S.S. San Diego and the California Naval Militia," California Center for Military History; U-Boat Net; "We Finally Know What Sank the U.S.S. San Diego During World War I," Smithsonian, 14 December 2018

Thanks to WWI Centennial Commissioner Jack Monahan for suggesting this article.