Denise Sharp is a go-to historian for her extended family, and her knowledge of the Sharp and Doerer clans of greater Baltimore is encyclopedic. But one question lingered in her mind for years.

Her late father, Donald Doerer, fought in Europe during World War II, and he rarely spoke about his experiences. But he did tell her about one day in the mid-1940s, when he visited the mother of a friend who was missing in action.

“He told me this poor woman cried out loud and said, ‘Why don’t we know anything about what happened to him? Why didn’t you protect him like you were supposed to?’ ” recalls Sharp, 66, who runs a 530-acre farm in Brookeville in Montgomery County.

“I never knew who that young man or his mother were,” Sharp said.

Now, thanks to the work of a determined documentary filmmaker, she has an inkling of their identities — and is learning the details of a catastrophe the U.S. military kept quiet for more than half a century.

She believes the young soldier in question was more than just a close boyhood friend of her father: He was his first cousin, Army Air Forces Sgt. Earle V. Hann Jr. of East Baltimore.

Newly available records show Hann was aboard the HMT Rohna, a transport ship sunk by a German bomber in a devastating attack off the coast of Algeria on Nov. 26, 1943.

A staggering 1,015 American soldiers lost their lives in the incident, making it the deadliest encounter at sea in the history of the U.S. military. But the U.S. War Department swore the nearly 700 survivors to secrecy under threat of court-martial, leaving the disaster all but unknown to the public for more than 50 years.

The decision didn’t just keep the fate of the Rohna out of the newspapers and history books. It left the parents of those killed — including Hann’s mother, Elizabeth Doerer Hann, who died in 1980 — in the dark about what had happened to their sons. Half a year went by before families received terse telegrams telling them their loved one was lost when a troop ship sank “as a result of enemy action.”

Knowing nothing more than that compounded the horror of the catastrophe, says Jack Ballo, the New Jersey-based filmmaker whose documentary in the making, “Rohna: Classified,” is bringing the story to life.

“That’s what happens when a terrible tragedy like this occurs and becomes classified, and when the War Department doesn’t share the truth with families,” he says. “This empty space goes down through the generations, and the truth gets lost. The film is about getting it to families like the Hanns and the Doerers who were denied the chance to learn it for so long.”

Ballo and a small team of researchers have been working on the film for nearly three years. They’re reaching out to families of victims and survivors, raising funds and compiling footage, and are aiming for a release date sometime next year. A portal on their website invites anyone who thinks they might have had a relative on the Rohna to contact them.

“It’s the most challenging project I’ve ever taken on. But as complicated as it has been, it’s probably been the one most worth doing,” Ballo said.

So much time has passed since World War II ended, and so little appetite did Sharp’s father and other returning veterans have for discussing the bloody conflict, that memories of men such as Hann have faded.

The fact that Hann, a radio operator, is coming into focus is due mainly to Ballo. He was clearing space in the attic of his wife’s family home four years ago, he says, when he came upon a cache of letters he’d never noticed before. They were written in the early 1940s by a young soldier in training, Joseph J. Pisinski, to his mother.

They were so heartfelt, Ballo says, that he had to investigate. He soon learned that Pisinski was his wife’s great-uncle and a soldier who had died at sea in World War II.

A Google search led him to the pages of “Rohna Memories: Eyewitness to Tragedy,” a self-published book by a Rhode Island videographer, Michael Walsh, who also had learned of the tragedy through a family member. Walsh’s father-in-law had been aboard the minesweeper USS Pioneer, which rescued 606 Rohna survivors, and Walsh tracked down and interviewed dozens of them.

The British Indian Steamship Company built the SS Rohna as a cargo and passenger ship in the 1920s, Walsh wrote. Once the war broke out, the British government commandeered it, renamed it HMT (His Majesty’s Transport) Rohna, painted it black and pressed it into service as a transfer ship for as many as 2,000 very cramped soldiers.

Allied forces made the “ugly, black, rusty old tub,” as one survivor later described it, part of a convoy of ships that left Bejaia, Algeria, on Thanksgiving 1943, bearing a young, untested, mostly American force toward the Suez Canal and beyond.

As the ships passed through a Mediterranean strait so dangerous it was known as Suicide Alley, Walsh wrote, about 30 German aircraft appeared from the West, the setting sun behind them, and began filling the sea with bombs.

All somehow missed, but a lone Heinkel He 177 circled back, bore in on the Rohna, and dropped what the Americans later learned was a cutting-edge weapon of war, a radio-controlled “glide bomb,” the Hs-293, that could change direction midair and track its target at 500 mph.

As survivors described it, some of the men on board thought the object was a broken-off piece of the aircraft, but the “thing” suddenly made a 90-degree turn, zoomed toward the ship, hit it at the waterline, tore a hole through both sides of the hull and exploded.

The impact killed an estimated 300 men instantly and left some 1,700 to scramble for the few working lifeboats or to dive into the choppy waters. The ship sank in 90 minutes, its undertow dragging many with it.

“I can’t get that picture out of my mind, these young guys, so green, the water around them everywhere, just flopping in the water, calling for their mothers, praying out loud,” says Walsh, whom Ballo recruited as a producer of the film. “It was a scary, scary situation.”

It marked the first successful deployment of a “smart bomb” against U.S. forces in history.

The few who have studied the attack argue over why the War Department, precursor to today’s Department of Defense, clamped down on the news. Some believe it was a ploy to preserve morale. Others say the brass wanted to keep the enemy guessing as to what the Allies learned from the missile’s use. Walsh believes the British government wanted to conceal how poorly equipped the Rohna was for its mission.

By the early 1990s, the U.S. government had declassified the incident, making official records available to researchers such as Ballo and Walsh.

In some of the Walsh film’s footage, survivors and their relatives discuss the incident and its aftermath in gripping detail. Darlene Panion Berube of Butte, Montana, says in one of the interviews that years after the war, she and her husband, Fred Panion, watched a war movie that included the sinking of a ship. Suddenly, Fred started crying.

“It’s all right, it’s only a movie,” she told him.

“That is something that happened to me,” he replied between sobs, and he proceeded to tell her for the first time his story of surviving the attack.

The husband and wife, who have since died, were among the people who created the Rohna Survivors Memorial Association, a nonprofit organization whose members have quietly met in almost every year since 1993.

The story of the Rohna has gained little national traction. No scholarly books have been published, and the incident has made few history texts. But as time has passed, more stories have emerged within families and in the press. Knowledge of what happened and the men who experienced it is expanding.

Just ask Robert Doerer and Tom Myers of Satellite Beach, Fla. Doerer, 90, a retired U.S. Army intelligence officer, is a younger brother of Denise Sharp’s father, and so he, too, was Earle Hann’s first cousin.

He was only 10 when Earle, whom he vaguely remembers as a “pleasant” young man, left for basic training. He was 12 in January 1944, when Hann’s family received an alarming and less-than-forthcoming telegram. Sgt. Hann had gone missing “in the Mediterranean area” two months earlier, it said, adding “no further information is available.”

“The story we heard was that Earle had been shot down somewhere in North Africa,” Doerer said. “ ‘Missing’ doesn’t mean ‘dead,’ so there was that hope. But time makes things disappear. People kind of stopped talking about it. I eventually figured [his body] was somewhere out there in the dunes.”

Last month, Doerer had the idea of asking his son-in-law, Myers, to do a bit of research on Hann. An online search led Myers, a retired FBI forensics specialist, to the documentary’s website. It was the first time any member of the extended family had heard of the Rohna or knew what had happened to Hann.

Further research led Myers to Find A Grave, a website that depicts burial sites. There he learned that Hann’s name is inscribed, with more than 3,000 others, on a memorial at the North Africa American Cemetery near Tunis.

A graduate of St. Elizabeth’s Parochial School, Hann attended and may have graduated from Baltimore City College. As of 1940, when he was 18, he lived with his father, Earle V. Hann Sr., a crane operator, his mother, Elizabeth Doerer Hann, and four younger siblings.

Hann apparently worked for four years as a clerk at St. Mary’s Seminary on Roland Avenue, and was already a member of the Maryland National Guard when he went on active duty in February 1941. Though he started as an infantryman, he transferred to the air corps a year later. He was sent to North Africa a month before the Rohna went down.

A June 8, 1944, article in the Evening Sun lists Hann among several Maryland servicemen killed in action. It also lists a widow, Mrs. Carolyn Hann, among his survivors. None of his living relatives remember the marriage.

Sharp was surprised to learn Hann’s story, she says, as she had never heard his name before this month. She plans to begin incorporating his life and story into family lore.

— Baltimore Sun