Witold Pilecki. Wikipedia

In the early days of World War II, most of the world was unaware of the horrors occurring inside Nazi Germany’s Auschwitz camp — until Polish army captain Witold Pilecki volunteered to figure out the camp’s inner workings.

On September 19, 1940, German SS troops did exactly what Pilecki was hoping for: They captured him on the streets of Warsaw and brought him to Auschwitz.

Pilecki spent the next two and a half years inside Auschwitz.

Pilecki described his emergence into Auschwitz as otherworldly, saying he "bade farewell to everything I had hitherto known on this earth and entered something seemingly no longer of it," The New York Times reported.

The true intent of Auschwitz became apparent to Pilecki very quickly.

Auschwitz was designed to kill.

Since Pilecki was assigned to intense labor outside of the camp, he was able to sneak out reports to Polish officers.

Witold Pilecki as a prisoner in Auschwitz. Jewish Virtual Library

Pilecki's reports became increasingly horrific.

"Over a thousand a day from the new transports were gassed. The corpses were burnt in the new crematoria," Pilecki wrote in his book, "The Auschwitz Volunteer."

By the time the Nazis began rounding up Europe's Jewish population and carting them off to death camps like Auschwitz, Pilecki's reports were too horrific for the underground Polish army to believe.

Prisoners in a Nazi concentration camp after their liberation by American troops on May 6, 1945. WIkipedia

"The underground army was completely in disbelief about the horrors,"Alex Storozynski, Kosciuszko Foundation president and executive director, told NPR.

"About ovens, about gas chambers, about injections to murder people — people didn't believe him. They thought he was exaggerating," Storozynski added.

And while no orders came to destroy the camp, Pilecki wrote, "further stay here might be too dangerous and difficult for me" and planned his escape.

In the middle of the night on April 26, 1943, Pilecki escaped with Jan Redzej and Edward Ciesielski, two other prisoners, from the back door of a bakery.

According to Vice, here's how Pilecki, Redzej and Ciesielski escaped:

"Redzej had already used fresh bread to make an imprint of the nut holding the hook of the door, and they had made sure they had the right wrench to open it.

Under their striped prison uniforms, Pilecki and Ciesielski wore civilian clothes. They also took tobacco with them to scatter behind them, so that dogs couldn’t track them."

After his escape, Pilecki rejoined the army and wrote the first intelligence report about Nazi Germany's Auschwitz concentration camp.

In 1945 Pilecki agreed to gather intelligence for Poland about the Soviets and was eventually caught by the Polish Communist regime.

Witold Pilecki's mug shot. Wikimedia Commons

Following a trial, Pilecki was charged with espionage and executed on May 25, 1948, at Warsaw's Mokotow Prison.

According to NPR, there's a reason why most have never heard Pilecki's story of infiltrating Auschwitz.

After the war, "the communist regime in Poland censored any mention of his name in the public record, a ban that remained in place until the fall of the Berlin wall," NPR reported.

Amanda Macias contributed to this report.