Degenhardt grew up in Hagen, where he attended the humanistic Albrecht Dürer "Gymnasium". He belonged to the Catholic youth group, Bund Neudeutschland. As a member of this youth organisation, which was banned by the Nazis, he was arrested by the Gestapo in 1941, when he co-organised a demonstration of young people to show loyalty to the new spiritual leader, Lorenz Jaeger, on the day of his consecration as the Bishop of Paderborn. Degenhardt had already been suspected by the Gestapo for some time, since he had risked his life by secretly circulating the sermons of the Münster Bishop Clemens August Graf von Galen. He was held in solitary confinement for several weeks in the Dortmund Gestapo headquarters, imprisoned in a 3 x 1.5 m cell, beaten by the guards and not released until Christmas of 1941, with the warning that he would be sent to a concentration camp if he said anything about his imprisonment. After his release, he was expelled from the "Gymnasium". During the Second World War, he was conscripted as an aid in the Luftwaffe and was taken as a prisoner of war, from which he was released in 1946. After the War, he completed secondary school and studied philosophy and theology in Paderborn and Munich. On 6 August 1952 he was ordained as a priest by Archbishop Lorenz Jaeger in the Paderborn Cathedral.