Leisner was born on 28 February 1915, the oldest of five children. When he was six years old, the family moved to
Kleve, a city on the lower Rhine, where his father worked as a civil servant. He attended school and completed his
gymnasium studies in 1934. During his youth, he became an
altar boy and, at the suggestion of the high school chaplain, formed a Catholic youth group, the Saint Werner Group. These youth groups combined prayer with outdoor activities, such as camping and cycling. Leisner turned out to be a natural leader and became a youth leader in the 1930s, during the era in which the Nazis were beginning to take control of all youth organizations. In order to avoid Nazi interference, Leisner would often take his group on camping trips to Holland or Belgium. In 1934, when he was nineteen, Leisner entered the seminary in
Munich, and was named Diocesan Youth Leader by
Clemens August von Galen,
Bishop of Münster. He spent six months in compulsory agricultural work during which, despite Nazi opposition, he organized Sunday Mass for his fellow workers. In 1937, his parents' house was raided by the Gestapo, who seized his diaries and papers. These meticulously preserved documents tell how the spiritual young man became a religious leader. On 25 March 1939, Galen ordained Leisner a
deacon. Leisner was initially imprisoned in the
Sachsenhausen concentration camp, but was moved to the
Dachau concentration camp on 14 December 1940, where he became prisoner No. 22,356. Since he was a deacon, Leisner was assigned to the priests' block. On 17 December 1944,
Gaudete Sunday, a fellow prisoner, French Bishop
Gabriel Piguet, secretly ordained him a
priest. The necessary paperwork with the authorization for the ordination, as well as other necessary items, were smuggled into the camp by "
Mädi", the "Angel of Dachau", a young woman named Josefa Mack. (Mack went on to become a
School Sister of Notre Dame in Munich, called Sister Maria Imma.) Some imprisoned Protestant pastors helped organize the event and a Jewish violinist played music near the barracks to create a diversion. The newly ordained priest only celebrated a single Mass and was so ill that he had to postpone his first Mass for over a week. When Dachau was liberated on 4 May 1945, Leisner was taken to a sanatarium in
Planegg, near Munich. He died there a few months later, on 12 August 1945. Leisner's body was taken to Kleve and buried in a local cemetery on 20 August 1945. His remains were exhumed and re-interred in the crypt of the
Cathedral of Xanten in 1966. ==Beatification==