The German Naval Attack on Orleans, Cape Cod, Massachusetts. July 21, 1918.

On this day in 1918 the large U-156 surfaced off of Orleans, Massachusetts and took shots at the tugboat Perth Amboy and the four barge it was towing, damaging the barge and sinking all four barges.  The U-boat also shelled the town with its deck guns.

The U156 was a Type 151 German submarine, the same type as this captured example on display in the UK following World War One.  These were abnormally large U-boats that had originally been designed to be merchant blockade runners.  Note the two deck guns.

During the attack, a Surfboat was launched by the United States Life Saving Service, which is now part of the Coast Guard, to rescue the sailors trapped on the tug and the barges and came under shell fire from the submarine as well.

Curtis HS.

Shortly, the Navy dispatched Curtiss HS flying boats and Curtiss Model R bombers from Naval Air Station Chatham and they attacked the submarine.

Curtis Model R dropping a torpedo.

The entire incident was the only example of a German U-boat surfacing to attack a coastal target during the war, let alone bombarding a town.  What exactly the U-boat commander had in mind isn't known, as several weeks later the submarine disappeared with all hands.  Chances are, however, that commanding a large submarine with two deck guns, he simply chose to use them, and fairly successfully at that.