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They called Sgt. Henry Johnson "Black Death," a soldier from the all-black "Harlem Hellfighters" unit who fought off two dozen Germans with a gun and then a knife during World War I.

But when the war ended and the lauds from President Theodore Roosevelt and the French, who awarded him their nation’s highest award for valor, the "Croix de Guerre avec Palme," faded into the recesses of American history, Johnson couldn’t even get a pension. It was an era of racial segregation and Johnson, who spoke out against racism in the Army in a 1919 speech, died at age 32 after having spent his post service career as a porter for the rail service.

Now, nearly a century after his efforts in battle, the White House announced this week that Johnson will receive the Medal of Honor. Johnson and another WWI veteran, William Shemin, a Jewish sergeant who lied about his age in order to serve, and eventually led a platoon in battle, will be awarded the nation’s highest military honor on June 2.

Shemin’s daughter will accept the award on his behalf. Johnson’s award will be accepted by Command Sergeant Major Louis Wilson of the New York National Guard.

For New York lawmakers, including former Sen. Alfonse D’Amato and New York Sen. Chuck Schumer, the quest to ensure Johnson’s efforts were recognized was a nearly twenty year saga requiring exhaustive research, getting legislation approved by Congress to waive the statute of limitations, and advocacy by historians.

Bill introduced for Henry Johnson Medal of Honor campaign - Times Union http://t.co/61XzZxpMg6 via @TimesUnion — Paul Tonko (@RepPaulTonko) September 11, 2014

"Sgt. Henry Johnson, an Albany resident and Harlem Hellfighter, is a true American hero, who displayed the most profound battlefield bravery in World War I, yet the nation for which he was willing to give his life shamefully failed to recognize his heroics, just because he was a black man," Schumer said in a statement.

"This century-old injustice finally made right will be a profound gesture that will rectify a sad chapter in American history. And our nation will finally say ‘Thank-you’ to Sergeant Johnson, and the countless other African Americans who put their lives on the line for a nation that failed to treat them with full equality before the law," Schumer said.

In the early 1900s, Johnson, who was living in Albany, New York, was inspired by the Army’s recruitment efforts to join an African American regiment nicknamed "the Harlem Hellfighters" to help with the campaign in Europe. Johnson and his comrades were deployed to Europe and given menial tasks like digging latrines.

But as France struggled to keep up its war efforts, Gen. John Pershing lent the French the "Harlem Hellfighters" with one bit of advice: Keep a close watch on the black soldiers because they are "inferior" to whites, according to the New York State Military Museum.

The French outfitted Johnson, who was a private at the time, and fellow soldier Needham Roberts, a private from Trenton, New Jersey, in French helmets and weapons, taught them a smattering of French phrases and sent them to an outpost at the edge of the Argonne Forest, according to Smithsonian Magazine.

It wasn’t long before Johnson heard the "snippin’ and clippin'" of Germans cutting the wire fences near the French camp. He and Roberts jumped into action and lobbed grenades into the night in the direction of German fire, according to historical accounts.

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Eventually, the two men were surrounded. Johnson swung his gun, which had jammed, at the enemy forces and when that broke and he was hit on the head, he whipped out a bolo knife and slashed a path for he and Roberts to escape.

"Each slash meant something, believe me," Johnson later said, according to historical records and Smithsonian Magazine. "I wasn’t doing exercises, let me tell you."

When it was all done, Johnson had killed four German soldiers and wounded roughly 20 more. He suffered 21 wounds during the melee and his effort helped hold the line against the Germans.

"There wasn’t anything so fine about it," Johnson would later say, according to the Smithsonian article. "Just fought for my life. A rabbit would have done that."

Johnson returned to his home country a hero and rode with the Harlem Hellfighters in a Fifth Avenue parade. He was also promoted to sergeant and the military used his likeness to recruit and sell war stamps with an ad campaign that read: "Henry Johnson licked a dozen Germans. How many stamps have you licked?"

But because his discharge papers didn’t mention his injuries, which included a severely damaged foot, or his battle efforts, Johnson never received a pension. Nor did he receive, at the time, the Purple Heart, which is awarded to those wounded in military service.

Johnson’s story faded into history.

Then, in 1999, a local historian and Vietnam veteran John Howe brought Johnson’s story to the attention of Schumer’s office, according to congressional aides.

Sgt. Henry Johnson's story is one of heroism and courage. Thanks to @SenSchumer he will get the honor he deserves. https://t.co/PwfeOjBw4P — Dan McCoy-CountyExec (@MCCoyCountyExec) May 15, 2015

Staffers struggled to find facts and information that were seemingly lost to history. Schumer took Johnson’s case to some of the highest levels of the Pentagon, office aides said, but the criteria for awarding the Medal of Honor is strict and without thorough documentation and after the death of Howe, the quest was stymied.

Then a few years ago, a young congressional staffer named Caroline Wekselbaum came across an article about Johnson. She asked about previous efforts and asked the senator and his staff if she could poke around on it.

She dug up records online that were thought lost and, because she did military casework for Schumer, she knew what the Army awards branch needed.

After a few weeks of intense searches, she found a communique from Gen. Pershing that few knew existed. Written shortly after the battle, Pershing reported Johnson’s acts and recommended him for bravery.

She then found other documents from Johnson’s foxhole buddy, Needham Roberts, and others who give the needed firsthand accounts.

Armed with this new evidence, Wekselbaum reworked the original Medal of Honor application.

"I loved working on this - it's very gratifying to see it actually happening after years of hard work by so many people, " Wekselbaum told NBC News.

The Army confirmed that new information used to approve Johnson’s award included battle accounts from his colleagues.

"After a formal review, it was determined that Sgt. Henry Johnson’s actions warranted approval," Army spokesman Wayne Hall told NBC News.

Johnson’s story has recently become more well known.

In the 1990s, Albany erected a monument to honor Johnson. The bust was placed in a traffic circle at the intersection of Henry Johnson Boulevard and Willett Street.

President Bill Clinton posthumously awarded Johnson a Purple Heart, and the story of the "Harlem Hellfighters" has been crafted into a graphic novel.

Johnson’s son, Herman Johnson, who was a major flew during World War II as part of the all-black Tuskegee Airmen, according to the Smithsonian, was thrilled to learn that his father was buried with full honors in Arlington National Cemetery. Herman Johnson died in 2004.

"It took years of exhaustive research to prove his claim, impassioned advocacy by local historians and by his relations, and legislation passed through both houses of Congress to waive the statute of limitations on his award to get this done, but the effort has finally paid off," Schumer said in a statement. "It will be one of my proudest accomplishments as senator to see our country’s highest military honor bestowed upon Henry Johnson."