During the Nazi occupation of Rome during the Second World War, he acted as an informal liaison between Pope Pius XII and the German leadership.
[1] Due to the outbreak of the First World War, the Salvatorian generalate moved from Rome to Fribourg, Switzerland.
[2] During the Second World War, Pfeiffer became an informal liaison between Pope Pius XII and the German leadership during the occupation of Rome by the Nazis in 1943 and 1944.
[2][7] On one occasion, the pope used Pfeiffer as an intermediary to speak with General Reiner Stahel, the commander of Nazi forces in Rome, and Heinrich Himmler, to secure the release of 249 Jews that had been rounded up.
[5][8] On another occasion, Pfeiffer persuaded the Nazis to release 400 hostages, eight of whom were Jews, who were being transported to their execution by firing squad.
[2][12] During the German retreat from Italy in 1945, Pfeiffer also convinced the Nazis to refrain from destroying several Italian cities.