Witold Pilecki has one of the most amazing stories from WWII. Pilecki fought with Polish forces against Nazi Germany and proposed the idea of smuggling himself into concentration camps to gain information.
At the time there was not much known about the camps, so in 1940 he snuck in pretending to be a Jew.Pilecki immediately began recruiting people for an underground resistance movement within the camp and reported the many atrocities being committed to those on the outside.
In fact, he is almost single handedly responsible for Britain and the United States receiving information about the planned extermination of the Jews and the purpose of the concentration camps.
Pilecki escaped Auschwitz in 1943 when he learned the Allies were not planning on liberating the camps right away and continued fighting in the name of freedom. After the war, Pilecki joined an anti-Communist group in Warsaw during Soviet occupation and was eventually captured and executed in 1948. His acts of bravery in the name of peace and freedom were not known until the fall of the Soviet Union in 1989.