At dusk, U-boat skipper Wolf Hans Hertwig spotted what he thought was a steamer heading north in the Bristol Channel, about 50 miles off the coast of Wales. It was a small ship with a single smokestack and two masts. Easy prey. He submerged to attack.

Through the periscope all he could see was a shadow of the vessel, but he was able to line up his shot. He set the running depth at 16 feet, estimated the range at 600 yards and fired a single 19-foot torpedo with a 350-pound warhead.

It struck amidships. Black smoke erupted, and two minutes later a secondary explosion threw up a “luminous” tower of water. Hertwig’s boat, UB-91, surfaced to look for wreckage or survivors. “Nothing found,” he recorded in the boat’s war diary.

Miles away, a radio operator with convoy H.G. 107, bound from Gibraltar to England, felt the shock of an underwater explosion. The USS Tampa, a Coast Guard cutter under Navy control, had just left the convoy, and headed alone for the Welsh port of Milford Haven to re-coal.

The “steamer” that Hertwig had destroyed, along with its entire crew, on Sept. 26, 1918, was the Tampa.

On Wednesday, at Coast Guard headquarters in Washington, the service is marking the 100th anniversary of the sinking of the Tampa, which was one of the single largest U.S. naval combat losses in World War I, and a crushing blow to the newly created Coast Guard.

“We will never forget the service and dedication of Tampa’s crew,” Coast Guard Commandant Adm. Karl L. Schultz, said in a statement last week, nor “the meaning of their sacrifice."

Hertwig’s torpedo claimed the ship and killed the 131 people on board — 111 Coast Guardsmen, four U.S. Navy sailors, and 16 British sailors and dockworkers.

Little was left but fragments. Doors, chairs and a piece of a mast with a life belt attached that read “Tampa” were later found floating in the water. Also spotted but not recovered was a body clad in underclothes and a Navy life jacket and watch cap.

Two weeks later, the remains of crewman Alexander Saldarini were found at sea. Two more bodies washed ashore on the coast of Wales. One was identified as Seaman James Fleury. The other was never identified, according to the Coast Guard. The rest were gone.

The ship’s loss was front-page news from Washington to Honolulu, and especially in Tampa, the ship’s namesake and hometown of many crew members.

“The Tampa Sunk; Local Boys Aboard,” the Tampa Daily Times announced when word got out. “Sinking . . . Brings War Home.”

Nineteen were from the Tampa area, the paper said: Among them were the Sumner brothers, Homer, 19, and Wamboldt, 24; the Mansfield brothers, Percy, 19, and Fred, 23; and their pals, brothers Algy Bevins, 23, and Arthur Bevins, 25.

Beyond Florida, Irving Slicklen, 15, of New York City was among the dead, according to Coast Guard researchers Nora L. Chidlow and Arlyn Danielson. He had wangled his way into the service apparently because he was tall for his age.

Also killed was Benjamin Nash Daniels, a 25-year-old machinist first class and the son of a lighthouse keeper. He had a wife and 3-year-old son back home.

Francis Leroy Wilkes, a 21-year-old African American seaman from Nantucket Island, Mass., perished. He was newly married and a descendant of the first enslaved family in Nantucket to gain its freedom. He had a brother, Roger, who was also in the Coast Guard.

Arthur Thomas Harris, 25, a sailor from Brooklyn, was killed. He had a college degree and worked at the old Bureau of Standards in Washington while doing postgraduate work at George Washington University.

Edward F. Shanahan Jr.'s father, Edward Sr., had just written him a letter from home in Jersey City three weeks before the sinking.

The elder Shanahan expressed approval of his son’s recent reenlistment: “These times one must be ready to make sacrifices.”

“Well, Ed, here’s hoping you have just as much luck in your new enlistment as you experienced in the first,” his father wrote. “In closing, let me remind you again, my son, of being careful of the acquaintances you make and to take the very best care of your self.”

The letter was returned unopened, and stamped “Man Lost” on the front.

A special calamity

U-boats sank thousands of allied ships during World War I (1914-1918). Most famous was the British ocean liner Lusitania, which went down in May 1915, killing almost 1,200 people. Thousands more sailors and civilians perished as the war went on and U-boats ranged as far as the Chesapeake Bay.

The day before UB-91 destroyed the Tampa, Kapitänleutnant Hertwig sank a British cargo steamer, the Hebburn, off the south coast of Ireland, with the loss of six lives, according to the website

On Sept. 30, U-152 attacked and sank the armed Navy cargo ship USS Ticonderoga. The 237 passengers and crew abandoned ship and most were set adrift. When they were rescued four days later, only 22 were alive. The dead included 112 American sailors and 101 soldiers, according to the Navy.

For the most part, largely because the United States didn’t enter the war until 1917, few American warships were hit. So the loss of the Tampa was a special calamity.

A last sighting

At noon on Sept. 26, the Tampa’s captain, Charles Satterlee, 43, a distinguished-looking member of an old Connecticut family, asked permission to leave the convoy. He was running low on coal.

But because of the danger of steaming alone in waters prowled by German subs, permission was denied, according to the Coast Guard researchers.

Four hours later, Satterlee was desperate and made the request again. This time it was granted. And the ship was last seen on the horizon heading for Milford Haven.

The Tampa had been on Atlantic convoy duty since October 1917, guarding allied cargo ships against attack from German subs and making 18 trips between Gibraltar and Britain, according to records in the National Archives.

There had been some brushes with the enemy. On Dec. 26, 1917, the Tampa had watched as UB 57 torpedoed two British steamers loaded with coal, the Benito and the Tregenna, off the south coast of Wales. Other times the Tampa fired on what were thought to be enemy submarines.

And there had been one fatal onboard incident.

On May 21, veteran crewman Albert H. Hahn was putting the muzzle cover on one of the deck guns after a drill when the gun went off. Hahn was struck in the right arm and chest and died within hours. Two days later his body was taken ashore “for preparation for burial or shipment to U.S.A.," according to surviving logs.

A sadness that carried

The ivory-colored box of old letters was always kept in an ottoman in the master bedroom of the Shanahan home in Northwest Washington, with wax paper between the sheets to protect them.

They were four wartime letters exchanged between the elder Shanahans and son Edward Jr., and saved by younger brother Joseph.

“My dad carried this sadness,” Kathy Shanahan Butler of Northwest Washington said of her father, Joseph. She remembers her parents reading them to her when she was a child and not realizing the tragedy the letters involved.

“My dad grieved so long for him,” she said last week. “He adored him. . . . Ed was just God.”

Two years ago, she made a pilgrimage to the Brookwood American Cemetery and Memorial outside London where the men of the Tampa are remembered.

Inside the columned stone chapel, light passes through elegant stained glass windows. And on the left, inscribed in stone, was her uncle’s name.

“Tears poured down my face,” she said. “It was just so overwhelming to touch his name. . . . I just kept putting my hand back and forth and back and forth,” she said. “Edward F. Shanahan Jr., Jersey City, New Jersey, that he was born, that he died, that he was a seaman.”

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