HMS H5 had been launched on 1 April 1915 at the height of the U-boat crisis -- one of a batch of small American-designed submarines built for the Royal Navy because British yards could not produce boats fast enough to meet the war's demand. She was 150 feet long, displaced 364 long tons on the surface, and carried a crew of 22. Two diesel engines for surface running, two electric motors for submerged. She could make 13 knots on top, 11 underwater. Four bow torpedo tubes, six 18-inch torpedoes, and a 6-pounder quick-firing Hotchkiss gun on the deck. On 14 July 1916 she had ambushed and sunk the German U-boat U-51 off the Ems estuary; 34 German submariners died, four survived. The H5 was a proven and aggressive boat. She was returning from a patrol that night in March 1918 when she met the Rutherglen.

The Rutherglen's lookouts saw what they expected to see -- a German submarine in the western approaches in 1918, where dozens of merchant ships had already been lost. The collision was not a careful identification followed by an attack. It was a glimpse of a black hull on a black sea, and the action of a master who had been told that ramming was the right response and that hesitation would cost the lives of his own crew. The submarine he hit was British. The decision was a tragedy of war -- not a crime, not negligence, but the kind of error that the conditions of the conflict made nearly inevitable. The H5 sank quickly. There were no survivors. The Admiralty's first concern, in the immediate aftermath, was the morale of the merchant marine: ships had been told to ram, and merchant captains had to keep ramming if the campaign against the real U-boats was to continue. The court of inquiry recommended that the H5's commanding officer, Lieutenant-Commander Allan Childers, be cited for his conduct -- but the recommendation was suppressed, and the merchantman's master was decorated, on the official line that he had sunk a U-boat. The truth was held back from the public for years.

Lieutenant Earle Wayne Freed Childs was a United States Navy officer assigned as observer aboard the H5. The United States had been in the war since April 1917, and American submariners were being attached to British boats to learn from the Royal Navy's hard-won experience. Childs was 27, from Pennsylvania, on detachment from the American submarine AL-2. When the Rutherglen rammed the H5, he became the first US submariner to die in the First World War. His name is engraved on the United States Navy Memorial at Annapolis. The Royal Navy commemorates all twenty-six men of the H5 on Panel 29 at the Royal Navy Submarine Museum. The wreck site in St George's Channel is a controlled site under the Protection of Military Remains Act of 1986 -- a war grave, not to be disturbed.

In 2010, on Armed Forces Day in Holyhead -- the nearest port to the spot in St George's Channel where the H5 went down -- a memorial plaque was dedicated to the twenty-six men who died that night. The plaque names the British crew and the American observer alongside them. It does not gloss over the cause. It calls the H5 a casualty of war, lost to friendly fire from a ship doing what wartime orders required. The conditions of the U-boat war had made the merchant captain's decision a hair-trigger one, and the result was a small boat full of men, sailors and one young American among them, going down in the cold dark of a Welsh sea. The wreck has been imaged by sonar. The hull lies broken on the sea floor. The Admiralty's careful concealment of the truth eventually unwound, decade by decade, until the full story was published. The men's names are now where they should be.