During World War II and the Nazi occupation he worked as a labourer, studying theology in secret.

In 1944 following a crackdown on religious teaching he was forced into hiding. Many of his friends went to concentration camps.

Continuing his studies after the war, he was ordained a priest in 1946. By 1964 he was Archbishop of Krakow and three years later he became a cardinal.

During these years he gained respect for his stand against Poland's Communist regime.