Kammala wannan jumlar: An zabi Eugenio Pacelli ya gaji Paparoma Pius XI a watan Maris
Taro na shekara ta 1939. Da yake ɗaukar sunan wanda ya riga shi a matsayin alamar ci gaba, ya zama Paparoma Pius XII kuma ya yi ƙoƙarin yin sulhu a lokacin yakin. Kamar yadda Holy See ya yi a lokacin pontificate na Paparoma Benedict XV (1914<unk>1922) a lokacin Yaƙin Duniya na I, Vatican karkashin Pius XII ya bi manufofin tsaka tsaki na diflomasiyya a duk lokacin Yaƙin Duniya na II; Pius, kamar Benedict, ya bayyana tsaka tsaki na Vatican a matsayin "rashin son kai". Bai gano 'yan Nazi ba a lokacin yakin da ya yi na wariyar launin fata da kisan kare dangi; kodayake shugabannin duniya da kungiyoyin yahudawa sun yabe shi bayan mutuwarsa a 1958 saboda ceton rayukan dubban yahudawa, gaskiyar cewa bai yi Allah wadai da abin da daga baya aka kira Holocaust ba ya lalata gadon sa.