Pope Pius XII (Italian: Pio XII), born Eugenio Maria Giuseppe Giovanni Pacelli (Italian pronunciation: [euˈdʒɛːnjo maˈriːa dʒuˈzɛppe dʒoˈvanni paˈtʃɛlli]; 2 March 1876 – 9 October 1958), reigned as Pope from 2 March 1939 to his death in 1958.
The Church experienced severe persecution and mass deportations of Catholic clergy in the Eastern Bloc. Pius XII was a staunch opponent of Communism and of the Italian Communist Party.
More information on the Wikipedia page [1], and the articles on Pius XII and Russia [2] and Pius XII and Poland [3]. The Vatican website page is [4].
Among other Encyclicals authored Luctuosissimi eventus, Laetamur admodum and Datis nuperrime.