Gentzen was arrested during the citizens uprising against the occupying German forces on May 5, 1945. He, along with the rest of the staff of the German University in Prague was subsequently handed over to Soviet forces. Because of his past association with the SA, NSDAP and NSD Dozentenbund, Gentzen was detained in a prison camp, where he died of starvation on August 4, 1945.[5][6]