The young German soldier has his rifle slung over his shoulder, a half-eaten sandwich in his left hand and a drinking cup in his right.

As he steps to the refreshment window, a woman in a white apron leans over the counter and puts a sprig of flowers in a buttonhole of his uniform. He looks dashing in his spiked helmet and trim mustache, and she glances at him as he moves on.

Then she looks up at the camera.

It is June 1915, nearly 11 months into World War I. The place is Thorn — modern-day Torun, in northern Poland. And the soldier, whose name and fate are unknown, is headed for the front lines and the killing machine of the Great War.

The moment was captured by a brash, cigar-smoking American filmmaker, Wilbur H. Durborough, and his cameraman, Irving G. Ries, who had motored to the action in a Stutz Bearcat flying a U.S. flag, the word “press” emblazoned on the car.

George Willeman and Lynanne Schweighofer of the Library of Congress look through one of the reels of the film “On the Firing Line With the Germans” at the library’s campus in Culpeper, Va., on Jan. 10. (Jahi Chikwendiu/The Washington Post)

The scene is part of a little-known documentary about the German army — filmed by Americans — that will be part of an exhibit on World War I being assembled by the Library of Congress this year.

April 6 marks the 100th anniversary of the U.S. entry into World War I in 1917.

[The World War I hero buried in the National Cathedral]

The library recently restored and digitized the silent film, which is believed to be the only existing, essentially complete World War I feature-length documentary made by Americans.

It is an hour and 48 minutes long.

Forgotten for decades, Durborough’s film, called “On the Firing Line With the Germans,” was discovered in a wine cellar of the estate of a Chicago businessman in 1985 and was eventually turned over to the library.

The footage, most of it on old nitrate film, was examined one frame at a time at the library’s audiovisual conservation center in Culpeper, Va.

It has striking scenes of youthful German soldiers before they became the enemy.

Durborough captured them in camp, peeling potatoes, marching through Berlin, recuperating in hospitals, and fighting in apparent and simulated battle scenes. Many of the images are extremely clear, and the faces of the men and women extraordinary.

[The maskmaker for the maimed]

He also captured scenes of Warsaw’s Jewish ghetto and vivid shots of Allied prisoners of war — British, Russian and French, some still wearing 1860s-style caps and uniforms.

There are shots of the German emperor, Kaiser Wilhelm II.

And there are scenes of Durborough — in the Stutz with cigar and driving goggles, shaking hands with German officers, chatting with German soldiers and standing in the trenches.

Indeed, Durborough, like the famous Civil War photographer Mathew Brady, appears in many of the shots he set up. “He just inserts himself everywhere,” said Lynanne Schweighofer, a Library of Congress preservation specialist who helped reassemble the film.

In mid-1915, the war, which lasted from 1914 to 1918, already had claimed tens of thousands of soldiers as Britain, France and Russia were locked in horrific conflict with Germany and its allies.

[The son of a bus mechanic preserved a hallowed WWI site]

The United States was still neutral. And although the Germans held some advantage in the fighting, they felt they were losing the public relations contest, according to a study of the documentary by film scholars James W. Castellan, Ron van Dopperen and Cooper C. Graham.

Meanwhile, in 1914, Durborough, a seasoned newspaper photographer from just outside Dover, Del., had been assigned by Chicago’s Newspaper Enterprise Association, a news service, to photograph the war.

Then 32, Durborough was an ambitious go-getter who had worked for the Philadelphia Inquirer and the Chicago Examiner. He had covered strikes and conventions, and had met Mexican revolutionary Pancho Villa.

He took the job but asked whether he could shoot moving pictures, too, even though he had little movie experience.

The association declined to pay for filming but said he was free to make a documentary, as long as it didn’t interfere with his photo assignment.

Durborough got a group of Chicago business executives to invest. They hired Ries, an experienced cameraman who spoke German, and bought the Stutz Bearcat, then one of the fastest cars on the road.

And with a green light from German authorities, who were hungry for good publicity, Durborough, Ries and the Stutz sailed for Europe in early 1915.

Faces and frames that survived

Deep in the film center’s underground vaults, built into a hillside in Culpeper, concrete vault No. 53 holds, among other rare films, 42 reels of Durborough’s documentary.

“This is all Durborough,” Geo. Willeman, the manager of the nitrate film vault, said recently as he gestured to multiple shelves.

The documentary and others made on highly volatile nitrate film are protected by fire alarms, smoke detectors and fire-suppression systems. The temperature is kept at 39 degrees, the humidity at 30 percent.

In late 2014, Schweighofer and colleague Valerie Cervantes began poring over the film, guided by research done by Castellan; Graham, a retired Library of Congress film curator; and van Dopperen, who had mapped out a likely sequence of the scenes.

“It had been a dream for many people to get this thing back together,” Willeman said. “Because there’s nothing else like it — an American film about the German army in World War I.”

But many scenes were repetitive, or captured on film that was damaged or in poor condition.

“We would . . . see which one was the least deteriorated, had the best ability to be copied or just the best image content — what survived in the best shape,” Schweighofer said.

The task was done using a hand-cranked frame viewer at a spartan “rewind bench” in a special nitrate film workroom decorated with images of movie stars. One expert would study the scenes, while another took notes on content and condition.

Once the best scenes had been selected, the film was sent to the library’s laboratory to be cleaned, repaired and stabilized. The film was then digitized.

“The thing to me was looking at the faces of the individual soldiers,” Schweighofer said. “You saw the same ones over again. You find yourself wondering what happened to them. And if they survived this war, did they survive the next war?”

Willeman noted one scene in which German soldiers are obviously singing and enjoying themselves as they gather in front of a railroad car around a man playing an accordion.

“These guys aren’t monsters,” he said. “They’re just guys. They’re like any other army. . . . A majority of these guys, a couple years after the film, were no more. They’re gone.”

Before it was over, World War I killed more than 2 million German soldiers.

Young men transformed

But in June 1915, everybody looks happy at the refreshment stand in Thorn, run by the Vaterländischer Frauenverein, a patriotic women’s group.

In the scene, about 20 minutes into the film, the women at the stand walk among the soldiers, who are heading for the Russian front, handing out flowers and snacks from baskets.

As the young soldier with the mustache moves along, a woman pours a drink into his cup, and another gives him a kiss on the cheek.

He looks about 20, and after the kiss he disappears from the frames.

The man was one of thousands of soldiers Durborough and Ries filmed — most of them young, well-groomed and in clean uniforms, untarnished by combat they probably had not yet experienced.

It is only near the end of the film that the soldiers look grimy, tired and unshaven, in the wake of a battle. Durborough has extensive footage of ruined towns and refu­gees packed into rickety wagons on muddy roads.

And it is there that Durborough stops appearing in the film.

“Suddenly he vanishes,” Willeman said. “But you could see how important this has become to him, because he just goes on and on and on and on to show what’s happened.”

After the war

Durborough and Ries got back to the United States on Sept. 30, 1915, according to Graham, Castellan and van Dopperen’s study of the film.

The film was first shown two months later, in Milwaukee on Nov. 28. It began a long run in Chicago that December.

Newspaper ads described it as “The Motion Picture Scoop of the War!” Durborough often appeared at the showings and gave lectures. One promotional poster featured a portrait of the kaiser.

From Chicago, it began runs in theaters across the country. In Philadelphia in early 1916, Durborough arrived in the Stutz, driving it up and down in front of the theater where the film was showing, firing a gun to get attention.

Interest in the film evaporated in 1916 and 1917 as tensions with Germany rose. The United States declared war in April 1917.

During the war, Durborough served as an Army public relations officer.

Afterward, he gave up filmmaking and pursued various jobs in newspapers and public relations.

He was the art director and head of photography at the Philadelphia Evening Bulletin in the mid-1920s. He left the paper in 1926 and launched several failed business ventures, including one as a medicine salesman.

In 1931 his house outside Philadelphia went to a sheriff’s sale, according to Graham, Castellan and van Dopperen.

Durborough moved to Utah, then California, and died suddenly in San Bernardino in 1946 at age 63.

Ries, for his part, stayed in the film business as a cinematographer and special-effects expert. He was nominated, with two others, for an Academy Award for special effects in the 1956 science fiction movie “Forbidden Planet.” He died in 1963.

The Stutz wound up in storage in a barn in suburban Cleveland and was sold off at auction during the Depression.

Before he died, Durborough began outlining a novel based on his life.

“You go many places very far away,” he wrote. “You go in much danger. No harm comes to you. You will be old man. . . . You have happy life, then unhappy life, then in end happy again.”