*Watch the awards ceremony in the video above.

(The Hill) — Three of the seven known surviving members of a secret group during World War II accepted Congressional Gold Medals on Thursday.

Speaker Mike Johnson (R-La.) was scheduled to host the three members of the Ghost Army for the ceremony at the Capitol, more than 75 years after they served.

Here’s what you need to know about the Ghost Army:

What was the Ghost Army?

The Ghost Army included about 1,100 soldiers in the 23rd Headquarters Special Troops and the 3133rd Signal Company Special.

The group carried out 25 different “battlefield deceptions” in France, Luxembourg, Belgium, Germany and Italy during World War II, according to the Ghost Army Legacy Project website.

The soldiers’ mission included using inflatable tanks, trucks and planes, as well as sound effects, radio trickery, costume uniforms and acting, to trick the Germans on the battlefield.

For decades, their mission was kept secret. The Ghost Army Legacy Project called the troops “unsung heroes” because the details of their work were not known until they were declassified in 1996.

Operation Viersen was one of the Ghost Army’s biggest missions. In March 1945, the group drew German units away from a point on the Rhine River using “hundreds of inflatables” and sound trucks that operated for multiple nights. Fake headquarters were set up with officers “who were pretending to be colonels,” The Associated Press reported.

“This was an all-hand-on-deck affair, and it was completely successful,” Rick Beyer, a filmmaker who made a documentary about the operations, told The AP. “It fooled the Germans. They moved their troops to the river opposite where the deception was.”

Why are they receiving the award?

President Joe Biden signed the bipartisan, bicameral “Ghost Army Congressional Gold Medal Act” into law in February 2022. He said it would be an honor to recognize the Ghost Army for their “unique and highly distinguished service conducting deception operations in Europe during World War II.”

The Congressional Gold Medal is the highest distinction Congress can bestow.

Three of the seven known surviving members of the Ghost Army attended the ceremony.

Seymour Nussenbaum, of Monroe Township, New Jersey, and Bernard Bluestein, of Hoffman Estates, Illinois, both 100, attended. John Christman of Leesburg, New Jersey, is 99 years old and also attended.

Want to learn more about the Ghost Army?

Beyer, a filmmaker and author, has helped highlight the Ghost Army’s story through his work as president of the Ghost Army Legacy Project, a nonprofit dedicated to “preserving and honoring” the soldiers’ work.

He produced and directed the documentary “The Ghost Army,” in 2013 and wrote the 2015 book “The Ghost Army of World War II,” The AP reported.

“I just want to make sure it’s not forgotten,” he said. “I think it’s a great use of ingenuity, creativity on the battlefield.”

Beyer said the Ghost Army’s operations likely saved thousands of lives.