[Anthony Acevedo] was one of 350 U.S. soldiers held at Berga an der Elster, a satellite camp of the Nazis' notorious Buchenwald concentration camp. The soldiers, working 12-hour days, were used by the German army to dig tunnels and hide equipment in the final weeks of the war. Less than half of the soldiers survived their captivity and a subsequent death march, he says.

Acevedo shows few emotions as he scans the pages of his diary. But when he gets to one of his final entries, the decades of pent-up pain, the horror witnessed by a 20-year-old medic, are too much.

"We were liberated today, April the 23, 1945," he reads.

His body shakes, and he begins sobbing. "Sorry," he says, tears rolling down his face. "I'm sorry."

Acevedo's story is one that was never supposed to be told. "We had to sign an affidavit ... [saying] we never went through what we went through. We weren't supposed to say a word," he says.

The U.S. Army Center of Military History provided CNN a copy of the document signed by soldiers at the camp before they were sent back home. "You must be particularly on your guard with persons representing the press," it says. "You must give no account of your experience in books, newspapers, periodicals, or in broadcasts or in lectures."