During the Nazi occupation of Poland, the Salesians tried to continue with their education and youth work, despite the ban on non-approved programmes, but on 23rd May 1943, twelve Salesians in Krakow were arrested by the Gestapo.

Fr Jozef Kowalski was sent to Auschwitz on 26th June, where he did all he could to encourage his fellow prisoners in Block 25, bringing them spiritual comfort and urging their will to survive; secretly administering the sacraments, talking to them about Don Bosco, and at least once, publicly giving absolution to all of the condemned at a mass execution.

He suffered beatings and humiliation for being a Catholic priest, and on 3rd July 1942, he was severely beaten and then drowned. He was 31 years old.

In his last letter to his parents, he wrote:

Do not worry about me; I am in God's hands. I want to assure you that I feel His help at every step. Despite the present situation, I am happy and completely at peace.

He was one of the 108 Polish martyrs who died at the hands of the Nazis, who were beatified on 13th June 1999 by St John Paul II, and we celebrate him on 29th May.