In 1940, a Polish underground operative named Witold Pilecki volunteered to be imprisoned at Auschwitz.

His job was to gather intelligence about activities at the camp and establish a daring resistance network inside. Pilecki remained imprisoned for over two and a half years, and witnessed Auschwitz transform into the Nazi's most notorious death camp. He tried to warn the world of the horrors he was witnessing, but the world didn't listen.

Video by Adrian Hartrick & Dominika Ożyńska

More from BBC Reel's 'Unheard Of' playlist: https://www.bbc.com/reel/playlist/unheard-of

#bbcreel #bbc #bbcnews