On September 19, 1940, as a volunteer, Lieutenant Colonel Pilecki allowed himself to be captured by the Germans during a roundup in Warsaw in order to be sent to Auschwitz two days later as Tomasz Serafiński. His heroic mission had two objectives: to gather intelligence on how the notoriously infamous camp operated and, if possible, to organize a resistance movement in collaboration with the Polish underground.

He spent two years and seven months in the camp, known as the "death factory." From there, he sent reports to the Main Headquarters of the Union of Armed Struggle of the Home Army about the situation in the camp. He also established a secret network called the Union of Military Organization, consisting of over eight hundred prisoners. He decided to escape from Auschwitz only in 1943. On the night of April 26-27, 1943, he escaped along with two fellow prisoners, Jan Redzej and Edward Ciesielski.

Posthumously, he was awarded the Commander's Cross of the Order of Polonia Restituta and the Order of the White Eagle. In 2013, he was promoted to the rank of Colonel. Many schools, scout troops, streets, and institutions bear his name today. There is also a Museum - House of the Pilecki Family in Ostrowi Mazowieckiej.

Monuments to Lieutenant Colonel Pilecki are erected throughout Poland. The one in Opole was created by Professor Marian Molenda, an employee of the Art Faculty at Opole University.