[2][3] In 1933 Kruczkowski became a full-time writer, moved back to Kraków and in 1935 wrote his first play, Bohater naszych czasów ('Hero of our Times').

[3] He also wrote essays published in leftist magazines and newspapers, and political brochures: Człowiek i powszedność ('Man and Daily Reality', 1936), W klimacie dyktatury ('In the Climate of Dictatorship', 1938), Dlaczego jestem socjalistą?

[3] After Nazi Germany's Invasion of Poland, in which Kruczkowski fought in the Polish Army as an officer, he was arrested and spent the war in a prisoner-of-war camp.

[3] His 1948 Odwety ('Retributions') was well received, but it was his 1949 Niemcy ('The Germans'), a drama addressing the issue of Germany's moral responsibility for World War II, that gained him international recognition.

[2] He was an active and vocal supporter of the new communist order in Poland, involved in politicizing the culture and in introducing the style and doctrine of socialist realism.