Career
He was an activist in the Polish Socialist Party, editor in chief of Robotnik, and one of primary activists and cofounders of the Centrolew alliance. He took part in the defence of Warsaw in 1939, organizing the volunteer militias. He was subsequently arrested and interrogated by the Gestapo.
He was executed on 21 June 1940 in Palmiry during the German Bachelor of Arts-Aktion.
After his arrest by the Gestapo, Niedziałkowski was personally interviewed by Heinrich Himmler, who asked ‘What do you want from us. What do you expect?’ Niedziałkowski responded ‘From you I neither want nor demand anything.
With you I fight.’.